In humans, what main role does the hormone PTH serve in relation to bone health?

The hormone parathyroid hormone (PTH) plays a crucial role in maintaining calcium homeostasis in the body, which directly affects bone health. When calcium levels in the blood drop, PTH is secreted by the parathyroid glands. One of its primary functions is to increase the reabsorption of calcium in the kidneys, which means the kidneys will retain more calcium rather than excreting it in urine, thereby helping to elevate calcium levels back to normal.

In addition to its actions on the kidneys, PTH also stimulates osteoclasts, the cells responsible for breaking down bone tissue. This process releases stored calcium into the bloodstream, further contributing to the increase in blood calcium levels. Thus, PTH effectively acts to ensure that sufficient calcium is available for important physiological functions, including bone mineralization and nerve function.

This role of PTH in enhancing calcium reabsorption and mobilizing calcium from bone stores underscores its importance in bone health, emphasizing that maintaining adequate calcium levels is critical for the integrity and strength of bones.