Which hormone is most involved in regulating blood calcium levels?

The regulation of blood calcium levels is primarily controlled by parathyroid hormone (PTH). PTH is secreted by the parathyroid glands in response to low blood calcium levels. Its primary functions include increasing the release of calcium from the bones into the bloodstream, enhancing the reabsorption of calcium in the kidneys, and promoting the activation of vitamin D in the kidneys, which then increases intestinal absorption of calcium.

Through these mechanisms, parathyroid hormone effectively raises calcium levels in the blood, making it the most significant hormone in the regulation of calcium homeostasis. This regulation is critical for various physiological processes, including proper nerve function, muscle contraction, and overall metabolic functions.

Other hormones like calcitonin, insulin, and growth hormone are involved in different physiological processes. Calcitonin, for example, works to lower blood calcium levels, but it plays a less prominent role compared to parathyroid hormone. Insulin is primarily involved in glucose metabolism, and growth hormone influences overall growth rather than specifically regulating calcium levels. Thus, parathyroid hormone is the key hormone that maintains calcium balance in the body.