Which hormone regulates blood levels of calcium?

The regulation of blood calcium levels is primarily managed by parathyroid hormone (PTH). This hormone is produced by the parathyroid glands and plays a crucial role in maintaining calcium homeostasis in the body. When blood calcium levels drop below a certain threshold, PTH is released, which works to increase calcium levels through several mechanisms.

First, PTH stimulates the release of calcium from bones into the bloodstream. It also increases the reabsorption of calcium in the kidneys, reducing the amount of calcium excreted in urine. Additionally, PTH promotes the conversion of vitamin D into its active form, which enhances the intestinal absorption of calcium from dietary sources.

This coordinated approach ensures that the body can effectively regulate calcium levels, which is vital for various physiological functions, including muscle contraction, nerve function, and maintaining healthy bones. Other hormones listed, such as luteinizing hormone, thyroid-stimulating hormone, and adrenocorticotropic hormone, do not have a direct role in calcium regulation, focusing instead on different aspects of endocrine function.