Drugs for Deficiency Anemias - Vocabulary

Key terms and concepts covering red blood cell development, iron metabolism, vitamin B12 deficiency, and folic acid deficiency based on Chapter 47.

Proerythroblasts

The earliest stage of red blood cell development in the bone marrow, characterized by a lack of hemoglobin.

Erythroblasts

The second stage of red blood cell development residing in the bone marrow, during which developing cells gain hemoglobin.

Reticulocytes

Immature erythrocytes that evolve after the erythroblast stage and leave the bone marrow to enter the systemic circulation.

Erythrocytes

Fully mature red blood cells circulating in systemic circulation.

Stages of Red Blood Cell Development

The four evolutionary stages of developing red blood cells: proerythroblast, erythroblast, reticulocyte, and erythrocyte.

Ferritin

A storage complex consisting of iron plus a protein, found within mucosal cells, the liver, and other tissues.

Transferrin

The plasma protein responsible for binding and transporting iron throughout the body.

Fate of Iron in the Body

The physiological movement of iron through absorption, transport via transferrin, utilization in circulating hemoglobin (70\text{--}80\text{\freeformat{\%}} of total), storage as ferritin (18\text{\freeformat{\%}}), incorporation into myoglobin (10\text{\freeformat{\%}}), and continuous recycling.

Myoglobin

The oxygen-storing molecule of muscle containing approximately 10\text{\freeformat{\%}} of total body iron.

Hemosiderin

Aggregated ferritin in the bone marrow; its absence is a primary hallmark of iron deficiency anemia.

Serum iron-binding capacity (IBC)

A laboratory measure of iron binding by transferrin; an increase in IBC indicates an increased amount of transferrin not carrying iron, signaling reduced iron availability.

Ferrous sulfate

The oral ferrous salt that serves as the drug of choice for treating iron deficiency anemia and preventing deficiency when dietary intake is insufficient.

Carbonyl iron

A pure elemental iron preparation consisting of microparticles that are absorbed slowly, offering therapeutic efficacy equal to ferrous salts with a lower risk of toxicity.

Cobalamins

Members of the vitamin $B_{12}$ family, consisting of large molecules that contain an atom of cobalt.

Intrinsic factor

A compound secreted by parietal cells of the stomach required for the efficient absorption of vitamin $B_{12}$ in the ileum.

Transcobalamin II

The transport protein that binds free vitamin $B_{12}$ in the blood for distribution to tissues, primarily the liver.

Pernicious anemia

Vitamin $B_{12}$ deficiency caused specifically by an absence of intrinsic factor, usually secondary to stomach surgery or atrophy of gastric parietal cells.

Megaloblasts

Oversized erythroblasts that appear in the bone marrow as a result of impaired DNA synthesis during vitamin $B_{12}$ or folic acid deficiency.

Macrocytes

Oversized erythrocytes that enter the circulating blood when growing red blood cell precursors are unable to divide due to deficient DNA synthesis.

Megaloblastic anemia

An anemia characterized by oversized erythroblasts in the bone marrow and oversized erythrocytes in the blood, caused by vitamin $B_{12}$ or folic acid deficiency.

Relationship of Folic Acid and Vitamin B12 to DNA Synthesis

The metabolic interaction where inactive folic acid is activated via a vitamin $B_{12}$-dependent pathway (or an alternate pathway when folic acid is given in large amounts) to enable DNA synthesis and cell maturation.

Enterohepatic recirculation

The process by which folate from the liver is excreted into the intestine, reabsorbed, and returned to the liver via hepatic-portal circulation, salvaging up to $200\,\mu\text{g}$ of folate per day.

Sprue

An intestinal malabsorption syndrome that decreases folic acid uptake, which can be corrected by high doses of oral folic acid.