What is one of the five key functions of the kidneys?

One of the five key functions of the kidneys is hormonal production. The kidneys play a crucial role in the endocrine system by producing and releasing several hormones that help regulate various bodily functions. For example, they produce erythropoietin, a hormone that stimulates the production of red blood cells in response to low oxygen levels. Additionally, kidneys regulate blood pressure through the renin-angiotensin-aldosterone system, producing renin as part of that process. This hormonal regulation is essential for maintaining homeostasis in the body, influencing blood volume, electrolyte balance, and overall fluid regulation.

Other options do not accurately represent the primary functions of the kidneys: the production of insulin is primarily a function of the pancreas, protein synthesis occurs mainly in the liver, and while vitamins are important for health, they are generally stored in the liver and are not a primary function of the kidneys.