{
  "id": "ferritin",
  "title": "Ferritin",
  "lang": "en",
  "source_lang": "en",
  "summary": "Ferritin is an iron-storage protein that supports cellular iron balance and serves as a blood biomarker of iron stores and inflammation.",
  "category": "science",
  "subcategory": "biology",
  "type": "concept",
  "aliases": [],
  "generated_at": "2026-10-13",
  "model": "pro/gpt-6.1-sol",
  "url": "https://aiwiki.page/en/ferritin/",
  "translations": {
    "zh-Hans": {
      "url": "https://aiwiki.page/zh/ferritin/",
      "json": "https://aiwiki.page/zh/ferritin.json"
    }
  },
  "sections": [
    {
      "heading": "",
      "text": "Ferritin is an iron-storage protein that helps maintain iron homeostasis by enclosing iron within a hollow molecular shell. In humans, the principal intracellular form consists of 24 heavy- and light-chain subunits, which cooperate in converting soluble ferrous iron into a stored ferric mineral. This arrangement provides an iron reserve while limiting the potentially harmful reactions of unbound iron. Ferritin also occurs in many other organisms, with variations in subunit composition, cellular location, and regulation. (pmc.ncbi.nlm.nih.gov)\n\nA small amount of ferritin circulates in blood, where its concentration is widely used as a biomarker of body iron stores. Low serum ferritin commonly indicates iron depletion, but elevated concentrations can reflect iron accumulation, inflammation, liver disease, or other conditions; ferritin measurements therefore do not identify a diagnosis in isolation. The protein connects molecular iron metabolism with laboratory medicine and population nutrition assessment, while its self-assembling shell has also become a platform for experimental biotechnology and vaccine development. (ncbi.nlm.nih.gov)"
    },
    {
      "heading": "Molecular architecture and terminology",
      "text": "Ferritin is an iron-storage assembly comprising a hollow protein shell and, when loaded, an enclosed iron-rich mineral. The iron-free shell is termed apoferritin, whereas holoferritin specifies the shell together with its mineral cargo; “ferritin” also commonly denotes the protein assembly irrespective of its loading state. These terms distinguish the container from its contents, rather than describing unrelated proteins. Serum ferritin denotes ferritin circulating in blood serum, not a separate class of iron-storage protein. Circulating ferritin is relatively iron-poor, so its presence does not imply that the blood contains fully mineral-loaded cages. (academic.oup.com)\n\nThe canonical cage contains 24 protein subunits arranged into an approximately spherical shell about 12 nanometers in outer diameter, surrounding a cavity about 8 nanometers across. The protein shell alone has a molecular mass of roughly 480–500 kilodaltons. Its characteristic octahedral rotational symmetry is designated \\(432\\), reflecting the arrangement of fourfold, threefold, and twofold symmetry axes. “Octahedral” describes the symmetry of the subunit arrangement, not a sharply faceted external shape. The 24 subunits can be identical or closely related but different chains; either arrangement can preserve the same basic cage geometry. (pmc.ncbi.nlm.nih.gov)\n\nEach subunit folds into a bundle of four long α-helices, conventionally labelled A–D, with a shorter fifth helix, E, near the carboxyl terminus. A relatively long loop connects helices B and C. Helix E lies obliquely to the principal bundle and contributes to contacts around the fourfold symmetry axes. Extensive helix–helix contacts between neighboring subunits stabilize the assembled shell. Consequently, the cavity is an architectural property of the complete 24-subunit complex, rather than a pocket within an individual polypeptide chain. (nature.com)\n\nNarrow channels traverse the shell at the interfaces surrounding its symmetry axes. In canonical mammalian ferritin, there are eight threefold channels, each formed where three subunits meet, and six smaller fourfold channels formed around the terminal E helices of four subunits. The threefold channels contain predominantly hydrophilic amino-acid residues, including conserved acidic residues that interact with metal ions, and constitute the principal entry route for ferrous iron. The fourfold channels are predominantly hydrophobic in mammalian ferritin. These chemically distinct interfaces mean that the cage is neither an impermeable container nor a shell with equivalent openings: channel geometry and lining residues constrain exchanges between the cavity and the surrounding solution. (nature.com)\n\nThe stored mineral is a hydrated ferric oxide/oxyhydroxide, with iron predominantly in the \\(+3\\) oxidation state. It is commonly described as ferrihydrite-like, rather than as metallic iron or a pool of freely dissolved ions. Mineral order, phosphate content, and internal morphology vary between preparations and organisms; electron-microscopy studies of human hepatic ferritin have revealed polycrystalline cores with multiple mineral domains. A maximum capacity of approximately 4,000–4,500 iron atoms per cage is commonly reported, but this is a nominal high-loading estimate, not a fixed composition or a universally demonstrated physiological limit. Individual particles can contain substantially less iron: one microscopy study of 103 ferritin cores estimated contents ranging from a few hundred to around 5,000 atoms. Shell abundance, iron content per shell, and total stored iron are therefore distinct quantities. (pmc.ncbi.nlm.nih.gov)"
    },
    {
      "heading": "Human subunits, genes, and intracellular variants",
      "text": "Human cytosolic ferritin contains two genetically distinct protein subunits: the heavy chain, encoded by FTH1, and the light chain, encoded by FTL. The designations H and L refer to their approximate molecular masses of 21 and 19 kilodaltons, respectively. Their products co-assemble into 24-subunit cages, generally containing both chain types rather than a fixed, universal H:L ratio. Thus, differences in subunit composition do not imply a different cage architecture. Recombinant human H and L chains can also assemble separately into homopolymers, providing experimental systems in which the functions of each subunit can be distinguished from those of mixed cages. (ncbi.nlm.nih.gov)\n\nThe heavy chain contains a dinuclear ferroxidase center: a catalytic site that binds two iron ions and promotes the conversion of ferrous iron, \\(\\mathrm{Fe}^{2+}\\), to ferric iron, \\(\\mathrm{Fe}^{3+}\\). The light chain lacks this center. Instead, carboxyl groups on its cavity-facing surface provide a chemical environment favorable to iron nucleation and mineral growth. These are complementary rather than mutually exclusive functions: H-chain homopolymers can form mineral cores, and L-chain homopolymers can accumulate iron in vitro, although without the rapid oxidation supplied by H-chain centers. Experiments with recombinant heteropolymers further show that L subunits influence iron turnover at H-chain catalytic sites and assist core formation; consequently, the behavior of a mixed cage cannot always be predicted by simply averaging the properties of the two homopolymers. (pmc.ncbi.nlm.nih.gov)\n\nSubunit proportions differ among tissues. Heart and brain ferritins tend to be H-rich, whereas liver and spleen ferritins are generally L-rich, consistent with differences between rapid iron processing and longer-term storage. The term isoferritin denotes ferritin forms distinguishable by composition and physicochemical properties, particularly their isoelectric points. H-rich forms are generally more acidic than L-rich forms, and an individual tissue can contain several isoferritins. In a 1977 study, Adrian Bomford and colleagues separated ferritins from three control and four iron-loaded human hearts: their isoelectric points ranged from 4.8 to 5.6, and the most acidic preparations contained the highest proportions of H subunits. Isoferritin therefore describes variation within the ferritin family, not a separate class of iron-storage cage. (pmc.ncbi.nlm.nih.gov)\n\nMitochondrial ferritin, encoded by FTMT, is a distinct intracellular variant rather than cytosolic H/L ferritin transported intact into mitochondria. Sonia Levi and colleagues described it in 2001, identifying an intronless gene on chromosome 5q23.1 encoding a 242-amino-acid precursor. Its amino-terminal targeting sequence directs mitochondrial import; processing removes the leader and produces an approximately 22-kilodalton mature subunit. This H-chain-like protein retains ferroxidase activity and assembles into ferritin shells. (pubmed.ncbi.nlm.nih.gov)\n\nExperiments reported by Barbara Corsi and colleagues in 2002 localized mature mitochondrial ferritin to the mitochondrial matrix, where it formed homopolymers rather than mixed cytosolic H/L cages. In transfected HeLa cells, the wild-type protein incorporated radioactive \\(^{55}\\mathrm{Fe}\\), whereas a construct with an inactivated ferroxidase center did not. Increased mitochondrial ferritin expression also retained more iron in mitochondria and reduced cytosolic ferritin abundance, demonstrating experimentally that this compartment-specific storage protein can alter intracellular iron distribution. (pubmed.ncbi.nlm.nih.gov)"
    },
    {
      "heading": "Iron uptake, oxidation, and mineralization",
      "text": "Ferrous iron, \\(\\mathrm{Fe^{2+}}\\), enters the ferritin cage through water-filled channels at its threefold symmetry axes, where three subunits meet. This is transport through a protein shell, not uptake across a cell membrane: the iron is already intracellular before it enters cytosolic ferritin. Acidic amino-acid side chains lining the channels provide transient binding sites that guide iron toward catalytic centers embedded in the subunits. Channel geometry matters as well as charge. In a 2015 study of frog ferritin, replacing channel residue Asp127 with the longer glutamate side chain narrowed the inner opening, abolished detectable formation of the normal catalytic intermediate, and slowed mineral formation, although the mutant still assembled into cages. (pubmed.ncbi.nlm.nih.gov)\n\nAt the heavy-chain ferroxidase center, two ferrous ions bind close together and react with molecular oxygen. This oxidation–reduction reaction changes iron from the ferrous to the ferric oxidation state, \\(\\mathrm{Fe^{3+}}\\). A transient peroxo-bridged pair of ferric ions forms before further rearrangement into oxygen-bridged products. Experiments published in 2017 with recombinant human ferritin containing approximately 20 heavy and four light chains measured an initial ratio of two oxidized iron atoms per oxygen molecule, with hydrogen peroxide generated during the reaction. The ferroxidase center therefore converts incoming soluble iron into mineral precursors; it is not itself the final storage compartment. (pubmed.ncbi.nlm.nih.gov)\n\nMineralization proceeds beyond the initial two-iron reaction. Ferric products undergo hydrolysis and form oxygen-linked assemblies that ultimately contribute to the hydrated iron oxyhydroxide core inside the cavity. In 2002, stopped-flow spectroscopy and chemical measurements of H-type ferritin showed that decay of the diferric-peroxo intermediate produced hydrogen peroxide, diferric complexes, and small polynuclear ferric clusters in parallel. These observations distinguish the rapid catalytic oxidation step from subsequent cluster formation and mineral growth: storing iron requires both a change in oxidation state and its incorporation into a larger, poorly soluble assembly. (pubmed.ncbi.nlm.nih.gov)\n\nThe cavity-facing protein surface helps organize the earliest mineral deposits. Although light chains lack the heavy-chain ferroxidase center, their glutamate-rich surfaces provide sites for iron-cluster assembly. In 2017, Cecilia Pozzi and colleagues used X-ray crystallography to follow iron loading of human light-chain ferritin crystals. After 60 minutes of exposure to a ferrous solution, they observed a triiron(III) cluster anchored by Glu60, Glu61, and Glu64; Glu57 participated in directing incoming iron toward the cluster. Replacing the three anchoring glutamates with alanine reduced the measured iron-oxidation rate, supporting the interpretation of this surface cluster as a mineral-nucleation site. These experiments used light-chain homopolymers, separating their contribution from heavy-chain catalysis. (pubmed.ncbi.nlm.nih.gov)\n\nSequestration limits the availability of ferrous iron for the Fenton reaction, in which iron and hydrogen peroxide generate highly reactive hydroxyl radicals. Ferritin chemistry nevertheless involves peroxide, rather than simply excluding oxidants. In the 2017 recombinant human heteropolymer experiments, the peroxide generated during oxidation reacted with additional ferrous iron without producing significant hydroxyl radicals under the tested conditions. As mineral accumulated, oxidation at its surface also contributed increasingly to iron deposition. These results demonstrate controlled iron oxidation and sequestration in isolated ferritin; they do not establish that ferritin prevents all oxidative damage in cells or that every loading condition follows identical reaction proportions. (pmc.ncbi.nlm.nih.gov)"
    },
    {
      "heading": "Regulation of ferritin synthesis and turnover",
      "text": "Cytosolic ferritin synthesis is controlled by iron-responsive elements (IREs), RNA stem–loop structures in the 5′ untranslated regions of heavy- and light-chain messenger RNAs. These elements bind iron-regulatory proteins, IRP1 and IRP2, which connect intracellular iron availability to translation initiation. Under iron-depleted conditions, IRP binding represses ferritin production. Reconstituted cell-free experiments reported by Nicola K. Gray and Matthias W. Hentze in 1994 showed that the IRE–IRP complex prevents recruitment of the 43S translation preinitiation complex, including the small ribosomal subunit, to the mRNA. Thus, the regulatory block occurs before synthesis of the ferritin polypeptide rather than through inhibition of an already assembled storage cage. (sciencedirect.com)\n\nWhen iron becomes available, repression is relieved and existing ferritin mRNAs can support increased protein synthesis. This is post-transcriptional regulation: an increase in ferritin production does not, by itself, imply an increase in ferritin mRNA abundance. Hentze and colleagues’ 1987 deletion and transfer experiments established that the human heavy-chain IRE was necessary and sufficient to confer iron-responsive translational control on an experimental construct. Regulation also involves changes in the repressors themselves. In iron-replete cells, an ubiquitin-ligase complex containing the substrate adaptor FBXL5 promotes IRP2 degradation; iron and oxygen depletion destabilize FBXL5, allowing IRP2 to persist. This protein-turnover mechanism helps couple ferritin translation to the cellular iron supply. (pubmed.ncbi.nlm.nih.gov)\n\nFerritin turnover is regulated through ferritinophagy, the selective delivery of ferritin to lysosomes for degradation. Nuclear receptor coactivator 4 (NCOA4) acts as a cargo receptor rather than as an iron-release enzyme. In 2014, Joseph D. Mancias and colleagues identified NCOA4 through quantitative analysis of proteins enriched in human-cell autophagosomes. Depletion of NCOA4 impaired ferritin delivery to lysosomes, inhibited its degradation, and reduced bioavailable intracellular iron. Subsequent experiments established direct binding between a C-terminal region of NCOA4 and heavy-chain ferritin, including a requirement for the surface residue arginine 23. A 2024 cryo-electron microscopy study resolved 16 NCOA4 amino acids at the heavy-chain interface and used targeted mutants to test the functional importance of that binding surface. Recognition of heavy-chain subunits thereby enables NCOA4 to target assembled ferritin cages containing both heavy and light chains. (nature.com)\n\nThe abundance of NCOA4 provides another iron-sensitive control point. In experiments published in 2015, excess iron promoted association of NCOA4 with the HERC2 ubiquitin ligase and its degradation through the ubiquitin–proteasome system. Lower NCOA4 abundance reduces ferritinophagy and favors retention of iron in ferritin. Under iron-deficient conditions, diminished HERC2-dependent turnover permits NCOA4 accumulation and promotes mobilization of stored iron, although NCOA4 itself also undergoes autophagic turnover. Experiments in cultured erythroid cells and zebrafish linked this pathway to iron utilization during erythroid differentiation and hemoglobin production. (pubmed.ncbi.nlm.nih.gov)\n\nCellular iron mobilization must be distinguished from iron-release reactions measured with isolated ferritin. In a 2006 study using iron-chelator-treated hepatoma, Caco2, and K562 cells, the loss of ferritin-bound \\(^{59}\\mathrm{Fe}\\) paralleled ferritin protein degradation, with respective half-lives of approximately 23, 16, and 11 hours. Inhibitors of lysosomal proteolysis or function slowed both processes, supporting lysosomal turnover as a route for recovering stored iron in these experimental systems. By contrast, purified ferritin can release iron in assays containing reducing agents and an Fe(II)-binding chelator such as ferrozine. Such assays establish the chemical accessibility of the mineral iron under defined conditions, but do not by themselves establish how intact cells mobilize their ferritin stores. (journals.physiology.org)"
    },
    {
      "heading": "Tissue storage, secretion, and circulating ferritin",
      "text": "The liver, spleen, and bone marrow are major human iron-storage compartments, with ferritin present in liver parenchymal cells and in iron-recycling macrophages. These stores are connected to the turnover of erythrocytes: macrophages engulf aging or damaged red cells, degrade their hemoglobin, and recover iron from the released heme. Heme oxygenase-1 liberates ferrous iron, which can either enter intracellular ferritin or be exported through ferroportin for further use. Human erythrocytes survive approximately 100–120 days, and macrophage recycling returns about 20–30 mg of iron daily to the circulation, supporting new hemoglobin synthesis in the marrow. Ferritin storage therefore buffers a substantial internal iron flow rather than simply accumulating newly absorbed dietary iron. (medlineplus.gov)\n\nFerritin and hemosiderin are related but distinguishable storage materials. Ferritin retains a defined protein shell surrounding its mineral core; hemosiderin comprises larger deposits containing aggregated ferritin and partly degraded iron-storage material associated with lysosomal processing. Direct evidence came from a 1985 study by M. P. Weir, G. A. Sharp, and T. J. Peters, who isolated both materials from human spleens removed from patients with transfusion-associated iron overload. Electron microscopy showed mean mineral-core diameters of 6.4 nm for ferritin and 5.7 nm for hemosiderin, with thinner, irregular protein shells in the latter. These observations supported formation of hemosiderin through partial proteolysis of ferritin and partial dissolution of its mineral core, rather than identifying it as another intact ferritin isoform. (pubmed.ncbi.nlm.nih.gov)\n\nCirculating ferritin is generally relatively iron-poor compared with tissue ferritin, but “iron-poor” does not mean invariably iron-free. In a 1978 study, F. M. Zuyderhoudt and colleagues compared serum and liver ferritin from eight patients with liver disease: reported mean iron contents were 5% for serum ferritin and 16% for liver ferritin, with substantial variation between individuals. A serum ferritin blood test measures the concentration of immunologically recognized ferritin protein using antibodies, not the amount of iron enclosed within circulating cages. Determining ferritin-associated iron requires a separate procedure, such as isolating ferritin and measuring its iron chemically. Consequently, protein concentration and mineral loading are distinct measurements; serum ferritin’s use as a biomarker of tissue stores does not depend on circulating cages themselves containing most of the stored iron. (pubmed.ncbi.nlm.nih.gov)\n\nExperimental evidence also distinguishes active ferritin secretion from passive release by damaged cells. In 2010, Lyora A. Cohen and colleagues characterized mouse serum ferritin and identified splenic macrophages and kidney proximal-tubule cells as possible cellular sources. Mouse circulating ferritin consisted predominantly of light chains, contained little iron, and showed no detectable glycosylation. Its light chains frequently had shortened carboxyl termini, producing a characteristic 17-kDa band also associated with lysosomal ferritin. Together with their secretion experiments, these findings led the researchers to propose a nonclassical lysosomal secretory pathway in mice. The proposed route and cellular contributions were findings from that species and experimental system, not a demonstration that all human serum ferritin follows the same pathway. (pubmed.ncbi.nlm.nih.gov)\n\nA different secretion mechanism was demonstrated in a human-derived cell model. In 2004, Sharmistha Ghosh, Sarah Hevi, and Steven L. Chuck increased ferritin light-chain expression in HepG2 liver-tumor cells using stable transfection or adenoviral delivery. The cells exported light chains through the classical secretory pathway, and some exported chains acquired N-linked carbohydrate groups. Cage assembly was not required before secretion, and a factor present in serum rapidly inhibited export. These results document regulated secretion by cultured hepatic cells under increased light-chain expression, whereas the mouse experiments support a lysosome-associated route. Neither experimental setting establishes a single universal secretion mechanism for circulating ferritin in humans. (pubmed.ncbi.nlm.nih.gov)"
    },
    {
      "heading": "Ferritin across organisms and related protein families",
      "text": "Ferritin occurs in animals, plants, and bacteria, while ferritin-like iron-storage proteins have also been isolated from particular fungi. Across these groups, conservation of three-dimensional architecture does not imply identical subunit sequences, intracellular locations, or regulation. Canonical ferritins assemble 24 subunits around a mineral-containing cavity: crystallographic analysis of soybean ferritin, published in 2010, demonstrated the same overall cage organization found in vertebrate and bacterial ferritins. Plant subunits nevertheless possess an additional N-terminal extension peptide, and their catalytic and mineral-supporting properties do not reproduce the mammalian division between heavy and light chains. The broader ferritin-like protein family also includes assemblies with different subunit numbers. (pmc.ncbi.nlm.nih.gov)\n\nPlant ferritin is principally associated with plastids, including the chloroplasts of green tissues and plastids in seeds. An N-terminal transit peptide directs the precursor into the organelle and is removed during maturation; the following extension peptide remains part of the mature subunit. Ferritin thereby provides a compartmentalized means of managing iron without exposing surrounding cellular components to unrestricted iron-driven chemistry. Localization is not exclusively plastidic: a 2010 study of Arabidopsis thaliana AtFER4 examined its role in mitochondrial iron management using cultured-cell knockout mutants, which showed increased hydrogen peroxide and reduced oxygen consumption. Plant regulation also differs from the mammalian cytosolic system: iron-responsive changes in ferritin transcription are prominent, rather than regulation being centered on iron-responsive-element control of translation. A 2001 study identified four Arabidopsis ferritin genes; under its experimental conditions, AtFer1 and AtFer3 responded strongly to excess iron, whereas AtFer2 was expressed in seeds and responded to abscisic acid rather than iron treatment. (pmc.ncbi.nlm.nih.gov)\n\nFungal examples should not be treated as evidence that all fungi use the same ferritin system. In 1996, Carl J. Carrano, Rudi Böhnke, and Berthold F. Matzanke reported two distinct ferritin-like iron-containing proteins from Absidia spinosa, one associated with spores and the other with mycelia. The purified mycelial protein contained two distinguishable subunit types of approximately 20 kDa and about 750 iron atoms per assembled molecule. Its heme-like absorption spectrum and N-terminal sequence similarities led the investigators to identify it as a bacterioferritin. This finding also illustrates that a protein-family name need not impose an absolute taxonomic boundary. (pubmed.ncbi.nlm.nih.gov)\n\nBacterial nonheme ferritins, commonly designated Ftn, and bacterioferritins, designated Bfr, share iron oxidation and mineral-storage functions but differ in their cofactors. The conventional Bfr cage contains 24 subunits and up to 12 heme groups between paired subunits; these hemes are distinct from the iron stored in its mineral core. The 1994 structure of Escherichia coli bacterioferritin showed each heme coordinated by methionine-52 residues contributed by two adjacent subunits. Heme participates in electron transfer during reductive mobilization of stored iron, rather than simply providing additional storage sites. Experiments published in 2024 further demonstrated functional coupling between heme and the ferroxidase center during iron release from E. coli Bfr. (pmc.ncbi.nlm.nih.gov)\n\nDps proteins, named for “DNA-binding protein from starved cells,” are related smaller cages rather than canonical 24-subunit ferritins. Typical Dps assemblies contain 12 subunits, measure approximately 9 nm across, and enclose a cavity about 5 nm wide. Their ferroxidase centers occur at subunit interfaces. In E. coli Dps, hydrogen peroxide drives iron oxidation much more rapidly than molecular oxygen, linking iron sequestration with peroxide removal. DNA association supplies an additional protective function in some members, but should not be assumed from the family name alone. A 2023 study of Pseudomonas aeruginosa Dps demonstrated peroxide-dependent ferroxidase activity and a contribution to bacterial survival under hydrogen-peroxide stress, while also finding DNA-cleaving activity in vitro. (pmc.ncbi.nlm.nih.gov)"
    },
    {
      "heading": "Laboratory measurement and population assessment",
      "text": "Serum or plasma ferritin is measured by immunochemical assays that recognize ferritin with specific antibodies. Methods include enzyme-linked immunosorbent assays, chemiluminescent immunoassays, immunonephelometry, and radioimmunoassays; the analytical signal is related to ferritin concentration through standards of assigned concentration. The result expresses the concentration of ferritin protein, not the mass of iron contained within its mineral cores. Laboratory and survey reports distinguish the specimen matrix and state the measurement units: nanograms per millilitre and micrograms per litre are numerically equivalent, \\(1\\ \\mathrm{ng/mL}=1\\ \\mathrm{\\mu g/L}\\). Serum and plasma are both acceptable matrices, but comparisons over time require consistency because specimen and assay differences can affect results. (iris.who.int)\n\nAssay calibration links instrument responses to international reference materials. The 2020 World Health Organization (WHO) guideline recommended traceability to its ferritin international standard, NIBSC code 94/572. This recombinant human ferritin preparation was evaluated by 18 laboratories in nine countries and assigned a content of 6.3 micrograms per ampoule. Traceability alone does not eliminate intermethod variation: a reference material must also be commutable, meaning that its behaviour across measurement procedures resembles that of patient specimens. WHO therefore emphasized consistent methods for follow-up, quality controls at low, medium, and high concentrations, and participation in external quality-assurance programmes. A laboratory reference interval describes the distribution in a selected healthy reference population; a diagnostic decision threshold addresses a defined disease or assessment question. Consequently, the lower boundary of a laboratory’s reference interval is not necessarily the threshold used to classify iron deficiency. (nibsc.org)\n\nThe WHO framework published in 2020 defines iron deficiency in apparently healthy children aged 0–59 months using ferritin below \\(12\\ \\mathrm{\\mu g/L}\\). For apparently healthy children aged five years or older, adolescents, adults, and older people, the corresponding threshold is below \\(15\\ \\mathrm{\\mu g/L}\\). “Apparently healthy” denotes physical well-being appropriate to age and physiological status, without detectable disease or infirmity. The guideline’s table specifies below \\(15\\ \\mathrm{\\mu g/L}\\) for the first trimester of pregnancy, rather than a single threshold throughout gestation. For individuals with infection or inflammation, its age-specific thresholds are below \\(30\\ \\mathrm{\\mu g/L}\\) in children under five and below \\(70\\ \\mathrm{\\mu g/L}\\) from five years onward. These values classify depleted iron stores under specified conditions; they do not independently establish anemia. (ncbi.nlm.nih.gov)\n\nInflammation can raise ferritin independently of iron stores, thereby lowering the apparent prevalence of deficiency if healthy-population thresholds are applied without adjustment. In settings with widespread infection or inflammation, WHO’s 2020 guideline specifies concurrent measurement of C-reactive protein (CRP) and α1-acid glycoprotein (AGP), which reflect different phases of the acute-phase response. Survey adjustment options include higher ferritin thresholds; exclusion of participants with elevated inflammatory markers; arithmetic correction factors for inflammation categories; and regression correction using continuous CRP and AGP concentrations. In the exclusion approach, elevated markers are defined as CRP above \\(5\\ \\mathrm{mg/L}\\), AGP above \\(1\\ \\mathrm{g/L}\\), or both. Regression models may additionally incorporate malaria infection as a binary variable. Adjusted concentrations can then be compared with thresholds for apparently healthy populations. (who.int)\n\nPopulation assessments use these classifications to estimate the proportion with depleted iron stores and to monitor nutrition interventions. Repeated surveys can compare iron-deficiency prevalence and ferritin distributions before and after an intervention, but changes in inflammation, specimen handling, or analytical methods can also change the measured outcome. WHO therefore calls for the same assay method and sample matrix when measuring intervention effects. Because different inflammation-adjustment approaches can produce substantially different prevalence estimates, survey comparisons depend on an explicitly identified, consistently applied adjustment procedure, as well as the age-specific decision thresholds. (who.int)"
    },
    {
      "heading": "Clinical interpretation of low and elevated concentrations",
      "text": "Low serum ferritin is evidence of depleted iron stores, but iron deficiency is not synonymous with iron-deficiency anemia. Storage iron can decline before the hemoglobin concentration falls; anemia denotes the additional reduction of hemoglobin below the appropriate population and laboratory threshold. The 2021 British Society of Gastroenterology guideline describes ferritin below 15 μg/L as indicating absent stores and concentrations below 30 μg/L as generally indicating low stores. Iron-deficiency anemia may also produce smaller, less hemoglobin-rich erythrocytes, reflected in reduced mean corpuscular volume and mean corpuscular hemoglobin on a complete blood count. These changes are not specific to iron deficiency: thalassemia, for example, can also cause microcytosis. (bsg.org.uk)\n\nFerritin is an acute-phase reactant, so its relationship to stored iron changes during inflammation. Activated macrophages and damaged liver cells can contribute to increased circulating ferritin; a normal or elevated result therefore does not exclude depleted stores. A related but distinct condition, functional iron deficiency, occurs when iron remains in storage cells but its supply to developing erythrocytes is inadequate. Hepcidin-mediated restriction of iron mobilization and intestinal absorption contributes to this pattern in chronic inflammatory disease. Absolute depletion and functional restriction can coexist, particularly in chronic kidney disease and inflammatory bowel disease. (www2.gov.bc.ca)\n\nInterpretation consequently combines ferritin with measurements addressing different biological questions. Hemoglobin and red-cell indices characterize anemia, while transferrin saturation indicates the availability of circulating iron. C-reactive protein provides evidence of an inflammatory context; soluble transferrin receptor and reticulocyte hemoglobin can provide additional information about iron demand and iron-restricted blood-cell production. In its 2020 guideline, the World Health Organization stated that ferritin below 70 μg/L in adults with infection or inflammation may indicate iron deficiency, a conditional recommendation based on low-certainty evidence. This inflammation-associated threshold is not a universal reference limit for healthy adults. (who.int)\n\nElevated ferritin may accompany genuine iron accumulation. In hereditary hemochromatosis, excessive intestinal absorption leads to tissue loading, especially in the liver, heart, and pancreas. Repeated blood transfusions provide another route to iron accumulation, including in transfusion-dependent thalassemia. However, liver injury, alcohol excess, fatty liver disease, infection, inflammatory disorders, renal disease, and malignancy can elevate ferritin without a corresponding increase in storage iron. The magnitude of the elevation alone does not reliably distinguish these causes: concentrations above 3,000 μg/L have been documented in both transfusional overload and severe inflammatory or hepatic illness. Transferrin saturation, transfusion history, liver measurements, and, in selected settings, iron-sensitive magnetic resonance imaging help distinguish tissue loading from other causes of hyperferritinemia. (medlineplus.gov)\n\nAge, sex, menstrual status, pregnancy, and chronic disease modify the interpretive context. Childhood and adolescent growth increase iron requirements, while pregnancy combines increased demand with plasma-volume expansion and changing inflammatory measures. WHO’s 2020 framework therefore specifies age- and physiological-status categories rather than a single “normal” range; its pregnancy threshold of 15 μg/L applies specifically to the first trimester. For otherwise healthy adults, concentrations above 150 μg/L in menstruating women or 200 μg/L in men and non-menstruating women were identified as possible indicators of iron-overload risk, not proof of overload. Laboratory reference intervals, deficiency decision thresholds, and overload-risk thresholds serve different purposes, and an isolated high ferritin result establishes neither the cause nor the extent of tissue iron accumulation. (who.int)"
    },
    {
      "heading": "Inherited disorders of ferritin",
      "text": "Hereditary hyperferritinemia–cataract syndrome (HHCS) is an autosomal dominant disorder caused by pathogenic variants in the iron-responsive element within the 5′ untranslated region of FTL, the gene encoding ferritin light chain. These variants affect a regulatory sequence rather than the protein’s amino-acid sequence. Normally, iron-regulatory proteins bind this RNA stem–loop when cellular iron availability is low, suppressing translation. Disease-associated variants weaken or abolish that interaction, allowing excessive light-chain synthesis despite limited iron availability. In 1995, Carole Beaumont and colleagues demonstrated loss of iron-regulatory-protein binding and constitutively increased light-chain production in cultured lymphoblastoid cells from an affected family. Serum ferritin elevation therefore reflects dysregulated protein production, not necessarily increased iron stores: another family reported in 1995 had concentrations of 950–2,259 μg/L without associated systemic iron overload. (nature.com)\n\nThe characteristic ocular lesion is a cataract containing crystalline deposits of light-chain ferritin. A 2000 investigation measured 147 μg of light-chain ferritin per gram of dry lens tissue in an affected lens, compared with less than 16 μg/g in a control cataract lens; the crystalline inclusions stained with antibodies against light-chain, but not heavy-chain, ferritin. Jamie E. Craig and colleagues’ 2003 study examined 26 affected individuals from four Australian kindreds. Lens abnormalities included slowly progressive flecks, vacuoles, and crystalline deposits, predominantly in the cortex but also in the nucleus. Eight of the 18 affected individuals examined ophthalmologically had undergone cataract extraction. Presentation was variable: one child had cataract at age two and a de novo regulatory variant, demonstrating that an affected parent is not required. (pubmed.ncbi.nlm.nih.gov)\n\nNeuroferritinopathy, also called hereditary ferritinopathy, is an autosomal dominant disorder associated with pathogenic variants in the FTL coding region. Its genetic basis was established in 2001. Unlike HHCS regulatory variants, neuroferritinopathy variants alter the light-chain polypeptide; several are nucleotide insertions that shift the reading frame and change its carboxyl-terminal sequence. Experimental expression of two pathogenic variants in HeLa and SH-SY5Y neuroblastoma cells showed that mutant chains coassembled with endogenous ferritin and reduced iron incorporation, a dominant-negative effect. Structural analysis of the p.Phe167SerfsX26 variant demonstrated disordered terminal sequences and disruption of the cage’s fourfold pores. These experiments connect altered ferritin structure with defective iron handling, while tissue pathology establishes the accumulation of iron and ferritin-containing inclusions in the nervous system. (pubmed.ncbi.nlm.nih.gov)\n\nThe established clinical phenotype is an adult-onset, progressive movement disorder. Chorea—irregular involuntary movements—and dystonia—sustained or intermittent abnormal muscle contractions—commonly begin in one or two limbs. A series of 40 individuals carrying the FTL c.460dupA variant had a mean onset age of approximately 40 years, with onset ranging from the second to seventh decades. Movement abnormalities often remain asymmetric while extending to additional limbs over five to ten years and becoming more generalized within approximately 20 years. Speech-related orofacial dystonia, impaired articulation, and swallowing difficulties are characteristic; cognitive and behavioral abnormalities can become prominent later. (ncbi.nlm.nih.gov)\n\nMagnetic resonance imaging reveals regional brain abnormalities consistent with iron accumulation, especially in the basal ganglia. Iron-sensitive sequences show reduced signal, while advanced disease can produce cystic degeneration or cavitation in the putamen and globus pallidus. Serum ferritin may nevertheless be low, particularly in affected males and postmenopausal females, and may remain within the reference interval in premenopausal females. Thus, the molecular contrast is between excessive production of structurally unchanged light chain in HHCS and production of functionally abnormal light chain in neuroferritinopathy; circulating ferritin concentration does not directly measure either ferritin’s storage competence or the amount of iron deposited in a particular brain region. (ncbi.nlm.nih.gov)"
    },
    {
      "heading": "Discovery and experimental investigation",
      "text": "In 1937, the Czech physiologist Vilém Laufberger isolated and named ferritin by crystallizing an iron-rich preparation from horse spleen. The material contained more than 20% iron by dry weight, tolerated heating to approximately 80 °C, and formed crystals with cadmium sulfate—properties that facilitated purification before modern chromatographic methods became available. This established ferritin as an isolatable substance rather than merely a histologically visible iron deposit. Leonor Michaelis and Samuel Granick subsequently investigated the relationship between its protein and iron components. Granick’s 1942 study characterized horse-spleen ferritin; their joint 1943 paper, Ferritin II. Apoferritin of Horse Spleen, described removal of iron to obtain apoferritin without destroying the protein. The separation distinguished a persistent protein framework from its variable iron content. Granick extended these investigations to physiological responses: a 1946 paper documented increased apoferritin in gastrointestinal mucosa following iron feeding. (pmc.ncbi.nlm.nih.gov)\n\nStructural investigation combined imaging with diffraction rather than relying on crystallization alone. Electron microscopy made the protein shell and its enclosed mineral observable as distinct components, while X-ray crystallography provided spatial information about the shell. In 1975, R. J. Hoare, Pauline M. Harrison, and T. G. Hoy reported a 6 Å electron-density map of horse-spleen apoferritin. They used two heavy-atom derivatives, prepared with parachloromercury benzoate and uranyl nitrate, to obtain the crystallographic phases needed to calculate the map. Studying apoferritin separated the problem of protein architecture from that of the mineral core; the diffraction measurements therefore complemented electron micrographs showing both components. (nature.com)\n\nBiochemical experiments then tested whether structural sites actually performed the functions assigned to them. A 1989 study, Identification of the Ferroxidase Centre in Ferritin, combined crystallographic evidence with site-directed mutagenesis of human heavy-chain ferritin. Measurements of ferroxidase activity identified a site within the subunit’s four-helix bundle as the catalytic center, present in heavy chains but not light chains. Altering a proposed functional site and measuring the resulting activity provided evidence beyond its appearance in a structure, helping distinguish the heavy chain’s catalytic contribution from other properties of the cage. (pubmed.ncbi.nlm.nih.gov)\n\nA separate experimental landmark concerned gene expression. On December 11, 1987, Matthias W. Hentze and colleagues published the identification of the iron-responsive element in the 5′ untranslated region of human heavy-chain ferritin messenger RNA. Deletion analysis established that this sequence was required for iron-dependent translational regulation. Inserting a synthetic DNA sequence encoding the element into an otherwise unresponsive construct transferred iron responsiveness to that construct, demonstrating sufficiency as well as necessity. The experiment localized regulatory information to the untranslated RNA leader, rather than the protein-coding sequence, and supplied a molecular basis for investigating iron-dependent control of ferritin synthesis. (pubmed.ncbi.nlm.nih.gov)\n\nRecombinant expression, targeted mutation, and cryo-electron microscopy also permit direct tests of ferritin’s interactions with cellular partners. A 2024 study reconstructed the complex between human heavy-chain ferritin and the ferritin-binding fragment of nuclear receptor coactivator 4 (NCOA4), resolving 16 NCOA4 amino acids at the interface. The structure explained how a solvent-exposed hydrophobic surface participates in recognition and clarified the importance of ferritin Arg23 and NCOA4 Ile489 and Trp497. Structure-guided ferritin mutants were examined with biophysical binding measurements and cellular interaction and localization assays; an engineered light-chain variant additionally tested the proposed basis of heavy-chain selectivity. These experiments connected an observed interface to measurable recognition, while specifically characterizing a binding fragment rather than the entire machinery responsible for ferritin degradation. (pmc.ncbi.nlm.nih.gov)"
    },
    {
      "heading": "Engineered ferritin cages and biotechnology",
      "text": "Ferritin’s self-assembling shell provides two separately addressable compartments for biotechnology: an internal cavity that can contain cargo and an external surface that can carry targeting groups or antigens. The canonical 24-subunit cage is approximately 12 nm across, with an approximately 8-nm cavity; this defined architecture constrains the dimensions of materials formed inside it. Genetic fusion can attach additional peptide sequences to individual subunits, while chemical conjugation modifies exposed functional groups. Engineered preparations can therefore combine encapsulation with surface display. These manufactured constructs—including recombinant cages, chemically modified apoferritin and particles containing non-native minerals—are distinct from naturally occurring circulating ferritin measured in blood assays. (pubmed.ncbi.nlm.nih.gov)\n\nCargo loading exploits either interactions with the cavity or controlled disruption and restoration of the shell. Xin Lin and colleagues demonstrated in 2011 that differently functionalized ferritin cages could be disassembled under acidic conditions and reassembled at pH 7.4, producing hybrid particles with multiple functions. Loading procedures are nevertheless preparation-dependent, and aggregation can reduce protein recovery. A 2017 study of doxorubicin encapsulation used hydrostatic pressure of 500 MPa at pH 5.5, together with 20 mM arginine, to suppress aggregation and achieve almost complete protein recovery. Stepwise decompression and subsequent incubation at pH 7.4 increased encapsulation; the resulting particles showed no notable drug leakage during two weeks of storage at 4 °C. These were experimental formulation and antitumor studies, not evidence of an established ferritin-based chemotherapy. (pubmed.ncbi.nlm.nih.gov)\n\nSurface engineering also permits experimental molecular imaging. Lin and colleagues’ 2011 platform combined an externally displayed RGD peptide for integrin binding, the fluorescent dye Cy5.5 and internally associated \\(^{64}\\mathrm{Cu}\\) for positron-emission tomography. The particles were evaluated in cell experiments and tumor-bearing mice, demonstrating that targeting, optical labeling and radionuclide loading could coexist in one cage. In a separate 2011 study, ferritin particles bearing both a fluorophore and a quencher acted as protease-activated probes: cleavage of an attached substrate restored fluorescence, and the system was tested in a mouse xenograft model. Such demonstrations establish loading and detection mechanisms under specified experimental conditions rather than clinical diagnostic performance. (pmc.ncbi.nlm.nih.gov)\n\nFor vaccines, ferritin serves as a repetitive antigen scaffold rather than principally as a cargo container. The H2HA-Ferritin construct fused the hemagglutinin ectodomain of the H2N2 influenza strain A/Singapore/1/1957 to a Helicobacter pylori ferritin subunit. Assembly produced eight hemagglutinin trimers arranged around the cage’s threefold axes. Katherine V. Houser, Grace L. Chen and colleagues reported its first-in-human, randomized, open-label phase 1 trial in February 2022. Fifty healthy adults aged 18–70 received either one 20-μg dose, two 60-μg doses, or a matched H2 DNA vaccine prime followed by a 60-μg ferritin-vaccine boost. (pmc.ncbi.nlm.nih.gov)\n\nThe trial’s primary endpoints concerned safety and tolerability; secondary endpoints measured antibody responses. Vaccination was reported as well tolerated, and exploratory assays detected neutralizing responses, including cross-reactive responses against H1 and H5 viruses in H2-naive participants. These immunological measurements did not establish protection against influenza illness. The small phase 1 study was not an efficacy trial, and its publication did not constitute regulatory approval of the vaccine. (nature.com)"
    }
  ],
  "links": [
    "protein",
    "homeostasis",
    "biomarker",
    "inflammation",
    "alpha-helix",
    "amino-acid",
    "ion",
    "oxidation-state",
    "spleen",
    "mitochondrion",
    "cell",
    "oxygen",
    "redox-reaction",
    "spectroscopy",
    "x-ray-crystallography",
    "catalysis",
    "messenger-rna",
    "translation-biology",
    "cryo-electron-microscopy",
    "bone-marrow",
    "macrophage",
    "erythrocyte",
    "hemoglobin",
    "electron-microscope",
    "blood-test",
    "antibody",
    "animal",
    "plant",
    "bacteria",
    "fungi",
    "chloroplast",
    "calibration",
    "world-health-organization",
    "pregnancy",
    "anemia",
    "prevalence",
    "c-reactive-protein",
    "nutrition",
    "complete-blood-count",
    "chronic-kidney-disease",
    "cancer",
    "magnetic-resonance-imaging",
    "gene",
    "cataract",
    "mutation",
    "gene-expression",
    "vaccine",
    "antigen",
    "influenza"
  ],
  "sources": [
    {
      "title": "Decoupling ferritin synthesis from free cytosolic iron results in ferritin secretion",
      "url": "https://pubmed.ncbi.nlm.nih.gov/21195349/"
    },
    {
      "title": "Crystal structure of the ferritin from the hyperthermophilic archaeal anaerobe Pyrococcus furiosus",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC1915633/"
    },
    {
      "title": "Cryo-EM structures and functional characterization of homo- and heteropolymers of human ferritin variants",
      "url": "https://www.nature.com/articles/s41598-020-77717-4"
    },
    {
      "title": "Crystal Structure of Plant Ferritin Reveals a Novel Metal Binding Site That Functions as a Transit Site for Metal Transfer in Ferritin",
      "url": "https://doi.org/10.1074%2Fjbc.M109.059790"
    },
    {
      "title": "3D morphology of the human hepatic ferritin mineral core: New evidence for a subunit structure revealed by single particle analysis of HAADF-STEM images",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC2832756/"
    },
    {
      "title": "Morphology of the ferritin iron core by aberration corrected scanning transmission electron microscopy",
      "url": "https://cronfa.swan.ac.uk/Record/cronfa49232/Download/49232__18458__29938688ccba46d980ead3ad40fa1e84.pdf"
    },
    {
      "title": "FTH1 ferritin heavy chain 1 [Homo sapiens (human)] - Gene - NCBI",
      "url": "https://www.ncbi.nlm.nih.gov/gene/002495"
    },
    {
      "title": "ferritin light chain [Homo sapiens] - Protein - NCBI",
      "url": "https://www.ncbi.nlm.nih.gov/protein/NP_000137.2"
    },
    {
      "title": "Iron Oxidation and Core Formation in Recombinant Heteropolymeric Human Ferritins - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5938754/"
    },
    {
      "title": "Variation in the distribution of two human heart ferritin species. Isoferritin profile and subunit composition in normal and iron-overloaded subjects - PubMed",
      "url": "https://pubmed.ncbi.nlm.nih.gov/588265/"
    },
    {
      "title": "A human mitochondrial ferritin encoded by an intronless gene - PubMed",
      "url": "https://pubmed.ncbi.nlm.nih.gov/11323407/"
    },
    {
      "title": "Human mitochondrial ferritin expressed in HeLa cells incorporates iron and affects cellular iron metabolism - PubMed",
      "url": "https://pubmed.ncbi.nlm.nih.gov/11953424/"
    },
    {
      "title": "Fe(2+) substrate transport through ferritin protein cage ion channels influences enzyme activity and biomineralization",
      "url": "https://pubmed.ncbi.nlm.nih.gov/26202907/"
    },
    {
      "title": "Iron Oxidation and Core Formation in Recombinant Heteropolymeric Human Ferritins",
      "url": "https://pubmed.ncbi.nlm.nih.gov/28636371/"
    },
    {
      "title": "Stoichiometric production of hydrogen peroxide and parallel formation of ferric multimers through decay of the diferric-peroxo complex, the first detectable intermediate in ferritin mineralization",
      "url": "https://pubmed.ncbi.nlm.nih.gov/12416989/"
    },
    {
      "title": "Chemistry at the protein-mineral interface in L-ferritin assists the assembly of a functional (μ3-oxo)Tris[(μ2-peroxo)] triiron(III) cluster",
      "url": "https://pubmed.ncbi.nlm.nih.gov/28202724/"
    },
    {
      "title": "Iron regulatory protein prevents binding of the 43S translation pre-initiation complex to ferritin and eALAS mRNAs",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC395301/?page=10"
    },
    {
      "title": "Identification of the iron-responsive element for the translational regulation of human ferritin mRNA",
      "url": "https://pubmed.ncbi.nlm.nih.gov/3685996/"
    },
    {
      "title": "Control of iron homeostasis by an iron-regulated ubiquitin ligase",
      "url": "https://pubmed.ncbi.nlm.nih.gov/19762596/"
    },
    {
      "title": "Quantitative proteomics identifies NCOA4 as the cargo receptor mediating ferritinophagy",
      "url": "https://www.nature.com/articles/nature13148"
    },
    {
      "title": "Ferritinophagy via NCOA4 is required for erythropoiesis and is regulated by iron dependent HERC2-mediated proteolysis",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4592949/"
    },
    {
      "title": "Ferritinophagy via NCOA4 is required for erythropoiesis and is regulated by iron dependent HERC2-mediated proteolysis",
      "url": "https://pubmed.ncbi.nlm.nih.gov/26436293/"
    },
    {
      "title": "Structural basis for the intracellular regulation of ferritin degradation",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC11076521/"
    },
    {
      "title": "Ferritin Blood Test: MedlinePlus Medical Test",
      "url": "https://medlineplus.gov/lab-tests/ferritin-blood-test/"
    },
    {
      "title": "Electron microscopic studies of human haemosiderin and ferritin.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/4031104/"
    },
    {
      "title": "Electron Microscopy of Hemosiderin: Presence of Ferritin and Occurrence of Crystalline Lattices in Hemosiderin Deposits",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC2224323/"
    },
    {
      "title": "On the iron content of human serum ferritin, especially in acute viral hepaptitis and iron overload.",
      "url": "https://pubmed.ncbi.nlm.nih.gov/719893/"
    },
    {
      "title": "A sandwich enzyme-linked immunosorbent assay for the quantitation of human plasma ferritin",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC6038846/"
    },
    {
      "title": "Serum ferritin is derived primarily from macrophages through a nonclassical secretory pathway",
      "url": "https://pubmed.ncbi.nlm.nih.gov/20472835/"
    },
    {
      "title": "Regulated secretion of glycosylated human ferritin from hepatocytes",
      "url": "https://pubmed.ncbi.nlm.nih.gov/14615366/"
    },
    {
      "title": "Role of H-1 and H-2 Subunits of Soybean Seed Ferritin in Oxidative Deposition of Iron in Protein",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC2952209/"
    },
    {
      "title": "Crystal Structure of Plant Ferritin Reveals a Novel Metal Binding Site That Functions as a Transit Site for Metal Transfer in Ferritin",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC2823546/"
    },
    {
      "title": "Protein Association and Dissociation Regulated by Extension Peptide: A Mode for Iron Control by Phytoferritin in Seeds",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC2971622/"
    },
    {
      "title": "AtFer4 ferritin is a determinant of iron homeostasis in Arabidopsis thaliana heterotrophic cells",
      "url": "https://pubmed.ncbi.nlm.nih.gov/20724023/"
    },
    {
      "title": "An Iron-induced Nitric Oxide Burst Precedes Ubiquitin-dependent Protein Degradation for Arabidopsis AtFer1 Ferritin Gene Expression",
      "url": "https://doi.org/10.1074/jbc.M602135200"
    },
    {
      "title": "Structure and differential expression of the four members of the Arabidopsis thaliana ferritin gene family",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC1222178/"
    },
    {
      "title": "Fungal ferritins: the ferritin from mycelia of Absidia spinosa is a bacterioferritin",
      "url": "https://pubmed.ncbi.nlm.nih.gov/8706873/"
    },
    {
      "title": "The extension peptide of plant ferritin from sea lettuce contributes to shell stability and surface hydrophobicity",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC3403414/"
    },
    {
      "title": "Characterization of the DNA-mediated Oxidation of Dps, a Bacterial Ferritin",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5014645/"
    },
    {
      "title": "Pseudomonas aeruginosa Dps (PA0962) Functions in H2O2 Mediated Oxidative Stress Defense and Exhibits In Vitro DNA Cleaving Activity",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC10002758/"
    },
    {
      "title": "WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations",
      "url": "https://www.who.int/publications/i/item/9789240000124"
    },
    {
      "title": "WHO GUIDELINE",
      "url": "https://iris.who.int/bitstream/handle/10665/331505/9789240000124-eng.pdf"
    },
    {
      "title": "WHO GUIDELINE",
      "url": "https://iris.who.int/bitstream/handle/10665/331505/9789240000124-eng.pdf?sequence=1"
    },
    {
      "title": "Table 1, Recommended cut-off values to define iron deficiency and risk of iron overload in apparently healthy and non-healthy individuals by age group",
      "url": "https://www.ncbi.nlm.nih.gov/books/NBK569877/table/fm-ch2.tab1/"
    },
    {
      "title": "EVIDENCE AND RECOMMENDATIONS",
      "url": "https://www.ncbi.nlm.nih.gov/books/NBK569876/"
    },
    {
      "title": "EXECUTIVE SUMMARY",
      "url": "https://www.ncbi.nlm.nih.gov/books/NBK569877/"
    },
    {
      "title": "WHO guideline on use of ferritin concentrations: Executive summary",
      "url": "https://www.who.int/docs/default-source/micronutrients/ferritin-guideline/ferritin-guidelines-executivesummary.pdf"
    },
    {
      "title": "WHO International Standard: Ferritin, human, recombinant, NIBSC code 94/572",
      "url": "https://nibsc.org/documents/ifu/94-572.pdf"
    },
    {
      "title": "Assessing the iron status of populations",
      "url": "https://iris.who.int/bitstream/10665/75368/1/9789241596107_eng.pdf"
    },
    {
      "title": "Distinguishing reference intervals and clinical decision limits: A review by the IFCC Committee on Reference Intervals and Decision Limits",
      "url": "https://pubmed.ncbi.nlm.nih.gov/30047297/"
    },
    {
      "title": "Ferritin",
      "url": "https://en.wikipedia.org/wiki/Ferritin"
    },
    {
      "title": "British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults",
      "url": "https://www.bsg.org.uk/getmedia/3e13dd5c-8e7b-4110-87c5-dcc1feee495d/Iron-Deficiency-Aneamia-in-Adults.pdf"
    },
    {
      "title": "British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC8515119/"
    },
    {
      "title": "WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations: Executive summary",
      "url": "https://www.who.int/docs/default-source/micronutrients/ferritin-guideline/ferritin-guidelines-executivesummary.pdf?sfvrsn=8c98babb_2"
    },
    {
      "title": "High Ferritin and Iron Overload – Investigation and Management",
      "url": "https://www2.gov.bc.ca/gov/content/health/practitioner-professional-resources/bc-guidelines/iron-overload%26amp"
    },
    {
      "title": "Hemochromatosis | Iron Overload | MedlinePlus",
      "url": "https://medlineplus.gov/hemochromatosis.html"
    },
    {
      "title": "WHO guidance helps detect iron deficiency and protect brain development",
      "url": "https://www.who.int/news-room/detail/20-04-2020-who-guidance-helps-detect-iron-deficiency-and-protect-brain-development"
    },
    {
      "title": "Mutation in the iron responsive element of the L ferritin mRNA in a family with dominant hyperferritinaemia and cataract",
      "url": "https://www.nature.com/articles/ng1295-444"
    },
    {
      "title": "Molecular basis for the recently described hereditary hyperferritinemia-cataract syndrome: a mutation in the iron-responsive element of ferritin L-subunit gene (the \"Verona mutation\")",
      "url": "https://pubmed.ncbi.nlm.nih.gov/7492760/"
    },
    {
      "title": "The lens in hereditary hyperferritinaemia cataract syndrome contains crystalline deposits of L-ferritin",
      "url": "https://pubmed.ncbi.nlm.nih.gov/10873976/"
    },
    {
      "title": "Hereditary hyperferritinemia-cataract syndrome: prevalence, lens morphology, spectrum of mutations, and clinical presentations",
      "url": "https://pubmed.ncbi.nlm.nih.gov/14662596/"
    },
    {
      "title": "Mutation in the gene encoding ferritin light polypeptide causes dominant adult-onset basal ganglia disease",
      "url": "https://pubmed.ncbi.nlm.nih.gov/11438811/"
    },
    {
      "title": "Oxidative stress and cell death in cells expressing L-ferritin variants causing neuroferritinopathy",
      "url": "https://pubmed.ncbi.nlm.nih.gov/19781644/"
    },
    {
      "title": "Unraveling of the E-helices and disruption of 4-fold pores are associated with iron mishandling in a mutant ferritin causing neurodegeneration",
      "url": "https://pubmed.ncbi.nlm.nih.gov/19923220/"
    },
    {
      "title": "Neuroferritinopathy — GeneReviews®",
      "url": "https://www.ncbi.nlm.nih.gov/sites/books/NBK1141/"
    },
    {
      "title": "A Brief History of Ferritin, an Ancient and Versatile Protein",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC11719527/"
    },
    {
      "title": "Ferritin; increase of the protein apoferritin in the gastrointestinal mucosa as a direct response to iron feeding; the function of ferritin in the regulation of iron absorption",
      "url": "https://pubmed.ncbi.nlm.nih.gov/21001168/"
    },
    {
      "title": "Identification of the ferroxidase centre in ferritin",
      "url": "https://pubmed.ncbi.nlm.nih.gov/2776883/"
    },
    {
      "title": "Chimeric ferritin nanocages for multiple function loading and multimodal imaging",
      "url": "https://pubmed.ncbi.nlm.nih.gov/21210706/"
    },
    {
      "title": "Chimeric ferritin nanocages for multiple function loading and multimodal imaging",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC3036786/"
    },
    {
      "title": "High hydrostatic pressure encapsulation of doxorubicin in ferritin nanocages with enhanced efficiency",
      "url": "https://pubmed.ncbi.nlm.nih.gov/28591619/"
    },
    {
      "title": "Safety and immunogenicity of a ferritin nanoparticle H2 influenza vaccine in healthy adults: a phase 1 trial",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC10588819/"
    },
    {
      "title": "Safety and immunogenicity of a ferritin nanoparticle H2 influenza vaccine in healthy adults: a phase 1 trial",
      "url": "https://www.nature.com/articles/s41591-021-01660-8"
    }
  ],
  "license": "https://creativecommons.org/licenses/by/4.0/"
}