What is the primary function of the parathyroid hormone?

The primary function of parathyroid hormone (PTH) is to regulate calcium levels in the blood. PTH is secreted by the parathyroid glands, which are located on the posterior surface of the thyroid gland. When blood calcium levels drop below a certain threshold, PTH is released into the bloodstream.

PTH plays a critical role in maintaining calcium homeostasis through several mechanisms. First, it acts on the bones by promoting the release of calcium into the bloodstream from bone tissue. Second, it enhances the reabsorption of calcium in the kidneys, reducing calcium loss through urine. Finally, PTH increases the activation of vitamin D in the kidneys, which in turn enhances intestinal absorption of calcium from the diet. This coordinated response effectively raises blood calcium levels, ensuring that they remain within a normal physiological range.

This accurate understanding of PTH's role is essential in recognizing how calcium levels are tightly regulated in the body and the potential implications of disturbances in this system on overall health.