Erythropoietin (EPO) is a hormone that plays a crucial role in the production of red blood cells. Red blood cells are responsible for carrying oxygen throughout the body. The given statement, option 'A', is true, which states that erythropoietin is a glycoprotein hormone. Here's an explanation of this statement:

Erythropoietin is a glycoprotein hormone:
- Erythropoietin is a glycoprotein hormone because it is a protein that contains a carbohydrate group attached to it. This carbohydrate group is responsible for the hormone's stability and function.
- Glycoprotein hormones, like erythropoietin, are typically produced and secreted by specialized cells in the body called endocrine cells.
- These hormones are involved in various physiological processes and act by binding to specific receptors on target cells, triggering specific cellular responses.

Erythropoietin production:
- Erythropoietin production is primarily regulated by the body's oxygen levels. When the oxygen levels in the body decrease, it stimulates the production and release of erythropoietin.
- Hypoxia, which refers to a low level of oxygen in the body, is a potent stimulus for erythropoietin production. Hypoxia can occur in conditions such as high altitude, lung diseases, or certain medical conditions that affect oxygen delivery to tissues.
- Erythropoietin is mainly produced in the kidneys, specifically in cells called peritubular interstitial cells, which are located in the renal cortex and outer medulla.
- However, small amounts of erythropoietin can also be produced in the liver and other tissues.

Function of erythropoietin:
- The primary function of erythropoietin is to stimulate the production of red blood cells, a process known as erythropoiesis.
- Erythropoietin acts on the bone marrow, specifically on the hematopoietic stem cells, which are the precursors of red blood cells.
- It promotes the proliferation and differentiation of these stem cells into mature red blood cells.
- Increased erythropoietin levels in the body result in an increased production of red blood cells, which helps to maintain adequate oxygen delivery to tissues.

In summary, erythropoietin is a glycoprotein hormone that is primarily produced in the kidneys. It is involved in the regulation of red blood cell production in response to low oxygen levels in the body.

Erythropoietin (EPO) is a hormone produced primarily by the kidneys, with small amounts made by the liver. Erythropoietin plays a key role in the production of red blood cells (RBCs) in the bone marrow, which carry oxygen from the lungs to the rest of the body.