What is the primary function of parathyroid hormone (PTH)?

The primary function of parathyroid hormone (PTH) is to regulate calcium levels and bone formation. PTH is secreted by the parathyroid glands and plays a crucial role in maintaining calcium homeostasis in the body. When blood calcium levels drop, PTH is released and acts on various target organs.

In the bones, PTH stimulates the activity of osteoclasts, which are cells that break down bone tissue, releasing calcium into the bloodstream. This process increases the level of calcium in the blood. In the kidneys, PTH enhances the reabsorption of calcium, while also promoting the excretion of phosphate, further contributing to the regulation of serum calcium levels. Additionally, PTH promotes the activation of vitamin D, which increases intestinal absorption of calcium.

By working through these mechanisms, PTH ensures that the body maintains adequate calcium levels necessary for various physiological functions, including muscle contraction, nerve function, and blood clotting, while also influencing bone remodeling processes.