Abbreviation: sTfR
A part of the transferrin 1 receptor that regulates endocytosis of transferrin-bound iron by erythroid cells of the bone marrow. Soluble transferrin receptor levels increase in conditions associated with erythroid hyperplasia (e.g., iron deficiency anemia, chronic hemolytic anemia) and decrease in conditions associated with erythroid hypoplasia (e.g., aplastic anemia, chronic renal failure).