How does the body regulate high blood calcium levels?

The regulation of high blood calcium levels primarily involves the secretion of calcitonin, a hormone produced by the thyroid gland. When blood calcium levels rise, calcitonin is released into the bloodstream, where it functions to lower those levels. It reduces the concentration of calcium in the blood by inhibiting the activity of osteoclasts, the cells responsible for bone resorption, which releases calcium from the bone into the bloodstream. Additionally, calcitonin increases the deposition of calcium in the bones and promotes the excretion of calcium through the kidneys, contributing to lower blood calcium levels.

Other mechanisms, such as parathyroid hormone secretion, are involved in increasing blood calcium when levels drop, while increasing calcium absorption in the intestines primarily enhances calcium levels rather than decreases them. Decreasing bone density is counterproductive to regulating high blood calcium levels, as it would lead to more calcium being released into the bloodstream. Thus, calcitonin plays a crucial role in the body’s ability to lower and regulate high blood calcium levels effectively.