Which hormone stimulates red blood cell production?

• A. Insulin
• B. Thrombopoietin
• C. Erythropoietin
• D. Adrenaline

Answer: (C)

Erythropoietin stimulates red blood cell production. It is mainly produced by kidney cells in response to low blood oxygen (hypoxia). When released, it travels to the bone marrow and binds to receptors on early erythroid progenitors, promoting their survival, proliferation, and maturation into red blood cells. This increases the blood’s capacity to carry oxygen. The system is regulated by oxygen levels: as oxygen delivery improves, erythropoietin production decreases.

Other options don’t drive erythropoiesis. Insulin regulates glucose metabolism, thrombopoietin stimulates platelet production, and adrenaline mediates the fight-or-flight response rather than red blood cell formation.