Skelet en Calcium Homeostase

Calcium is the most abundant mineral found in the human body.

A typical adult human body may contain up to 2 kg of calcium, of which about 99% is found in the skeletal system. So, the skeleton is a key component for calcium homeostasis—the regulation of calcium levels in the blood.

The key players in calcium homeostasis are calcitriol, parathyroid hormone, and osteoclasts.

Calcitriol, the active form of vitamin D, is an important regulator of the calcium level in the  blood.

But whenever the blood calcium level falls below normal, that is, below 9 to 11 mg/dl, the parathyroid gland releases parathyroid hormone.

The osteoclasts, stimulated by parathyroid hormone, increase the pace of calcium resorption from the bone matrix and release calcium into the blood.

Once the blood calcium increases to the appropriate level, parathyroid hormone secretion stops.

As osteoclasts resorb old and new bone matrix equally, severe calcium deficiency may cause brittleness in both old and new bones.

 On the other hand, unusually high blood calcium levels may lead to kidney stones.