What is the primary function of erythropoietin?

Erythropoietin is a hormone primarily produced by the kidneys that plays a crucial role in the production of red blood cells. When oxygen levels in the blood are low, the kidneys respond by releasing erythropoietin into the bloodstream, stimulating the bone marrow to increase the production of red blood cells. This process is essential for maintaining adequate oxygen delivery to tissues throughout the body.

While the other options indicate functions relevant to bodily processes, they do not pertain to the specific role of erythropoietin. For instance, controlling blood pressure involves various hormones and mechanisms that manage vascular resistance and blood volume. Regulating blood sugar levels is primarily associated with insulin and glucagon, which handle glucose metabolism. Supporting vitamin D synthesis relates to skin, liver, and kidney functions in activating the vitamin when exposed to sunlight. Thus, the distinct and primary function of erythropoietin is its stimulation of red blood cell production, which compensates for low oxygen levels, enhancing overall oxygen transport and cellular function.