What hormone is NOT produced by the kidneys?

Insulin is the hormone that is not produced by the kidneys. It is primarily produced by the pancreas, specifically by the beta cells of the islets of Langerhans. Insulin plays a crucial role in regulating blood glucose levels by facilitating the uptake of glucose into cells, thereby lowering blood sugar levels.

In contrast, the kidneys synthesize and release several important hormones. Renin is an enzyme that is secreted by the juxtaglomerular cells in the kidney in response to low blood pressure, and it plays a key role in the regulation of blood pressure and fluid balance. Erythropoietin is produced by the kidneys in response to low oxygen levels in the blood; it stimulates the production of red blood cells in the bone marrow. Calcitriol, the active form of vitamin D, is also produced by the kidneys and is important for calcium homeostasis and bone health.

Thus, the distinction lies in the fact that while the kidneys have significant hormonal functions, insulin is exclusively a product of the pancreas.