Which of the following is NOT a function of the kidneys?

The kidneys play a crucial role in maintaining various physiological functions in the body. Among their key responsibilities are the production of renin, which helps regulate blood pressure; fluid balance, ensuring the body maintains proper hydration levels; and the excretion of metabolic wastes, including urea and creatinine, from the bloodstream.

The production of insulin, however, is not a function of the kidneys. Insulin is a hormone that is produced by the pancreas and is essential for regulating glucose levels in the blood. While the kidneys may play a role in glucose homeostasis and can handle some aspects of glucose metabolism, the secretion of insulin is entirely the responsibility of pancreatic beta cells.

Thus, understanding the distinct roles of these organs clarifies why the function described in the answer choice is not attributed to the kidneys.