What regulates both phosphates and calcium levels in the body?

Parathyroid hormone (PTH) plays a critical role in regulating both phosphate and calcium levels in the body. It is secreted by the parathyroid glands in response to low serum calcium levels. When calcium levels drop, PTH is released, which stimulates several processes to increase calcium levels.

PTH increases the reabsorption of calcium in the kidneys, promotes the release of calcium from bones by stimulating osteoclast activity, and enhances intestinal absorption of calcium by stimulating the conversion of vitamin D to its active form. In terms of phosphate regulation, PTH causes a decrease in renal phosphate reabsorption, which leads to increased phosphate excretion in urine. This effect helps maintain calcium-phosphate balance in the body.

Other hormones mentioned do not have a direct or primary role in regulating both calcium and phosphate levels. Therefore, PTH is the key hormone responsible for maintaining the homeostasis of these essential minerals.