Iron Storage And Recycled Iron

Ferritin and hemosiderin are the primary storage forms of iron. These compounds are harbored in the liver, spleen, bone marrow, and skeletal muscle. Ferritin can be measured in plasma, while hemosiderin is more often identified in the urine or stained through the bone marrow. Iron stores in men are generally 1.0 to 1.4 g of body iron, and for women, 0.2 to 0.4 g. Given these figures and with the realization that the iron absorption requirement is on average 1 mg/day, it is easy to understand why in adults with iron-poor diets anemia may take years to develop. Specifically, body stores in men of 1 g.would last 3 to 4 years before iron depletion takes place.6 Indeed, most cases of iron deficiency are directly related to external blood loss, especially menorrhagia

The Iron Cycle: Ingestion, Absorption, Storage

Fe dietary intake.

Fe2+ and Fe3+ bound to transferrin or ferritin in whole blood plasma

Bone marrow Fe2+ and Fe3+ for hemoglobin synthesis or

Fe2+(Fe3+) in erythrocyte hemoglobin and recycled iron as red cells die

Storage Fe in cells as ferritin and heomsiderin

Fe dietary intake.

Fe2+ and Fe3+ bound to transferrin or ferritin in whole blood plasma

Bone marrow Fe2+ and Fe3+ for hemoglobin synthesis or

Fe2+(Fe3+) in erythrocyte hemoglobin and recycled iron as red cells die

Storage Fe in cells as ferritin and heomsiderin

Fe2 And Ferritin

Digestive System

Muscular System

Figure 5.1 The iron cycle: Ingestion, absorption, and storage.

Digestive System

Muscular System

Figure 5.1 The iron cycle: Ingestion, absorption, and storage.

or slow GI bleed. Blood lost outside the body has no chance of being recycled into the usable byproduct of heme and globin.

The recycling of iron from heme and amino acids from globin following the lysis of aged red cells is a very efficient process. Heme is returned to the bone marrow, and the amino acids of the globin chain are returned to the amino acid pool. Each of these products will later be recruited for hemoglobin formation and red cell production. In the adult, approximately 95% of recycled iron is used for red cell production, whereas in the infant, only 70% is used for this purpose (Fig. 5.2). Because of this relationship, it is easy to understand the significance of adequate iron sources in the early years of development.

Table 5.1 O The Multiple Forms of Iron in the Body

Iron in Food

Heme sources: Meat

Nonheme sources: Beans, clams, vegetables Iron in Storage

Ferritin: Found in liver, spleen, skeletal muscle, bone marrow

Hemosiderin: Found in excreted urine Iron in Circulation

Iron and globin are recycled as a result of red cell senescence

68 Part II • Red Cell Disorders

Table 5.2 O Enhancers of Iron Absorption

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Responses

  • mhret
    What is the main site for iron storage in the bone marrow?
    4 years ago
  • GERONTIUS
    Is the bone marrow the only storage of iron pool?
    1 month ago

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