Which hormone regulates blood calcium levels?

Calcitonin is the hormone that plays a crucial role in regulating blood calcium levels. It is produced by the parafollicular cells (also known as C cells) of the thyroid gland. When blood calcium levels rise above normal, calcitonin is released to lower those levels by inhibiting osteoclast activity in the bones, which decreases bone resorption and promotes the deposition of calcium into the bone matrix. Additionally, calcitonin enhances calcium excretion by the kidneys, further reducing the calcium concentration in the bloodstream.

In contrast to calcitonin, insulin is primarily involved in glucose metabolism, aldosterone regulates sodium and potassium balance primarily influencing fluid levels, and glucagon works to increase blood glucose levels. Each of these hormones has distinct roles that do not pertain to calcium homeostasis, underscoring the specific function of calcitonin in maintaining appropriate blood calcium concentrations.