Which hormone is known to increase blood calcium levels by affecting osteoclast activity?

Parathyroid Hormone (PTH) is the hormone responsible for increasing blood calcium levels by stimulating the activity of osteoclasts. Osteoclasts are specialized cells that break down bone tissue, releasing calcium into the bloodstream. PTH is secreted by the parathyroid glands in response to low blood calcium levels. Once released, it enhances the resorption of bone by osteoclasts, leading to an increase in plasma calcium concentrations.

This mechanism is crucial for maintaining calcium homeostasis in the body, as calcium plays vital roles in various physiological functions, including muscle contraction, nerve transmission, and blood clotting. In contrast to PTH, calcitonin works to lower blood calcium levels by inhibiting osteoclast activity and promoting calcium deposition in bones. Growth hormone primarily influences growth and metabolism rather than directly affecting calcium levels. Cortisol, a glucocorticoid, has various metabolic effects but does not primarily regulate blood calcium levels through osteoclast activity.