What is the role of the parathyroid glands?

The parathyroid glands play a crucial role in regulating mineral balance, especially calcium levels in the body. They achieve this by secreting parathyroid hormone (PTH), which is essential for maintaining serum calcium concentration within a narrow range. When calcium levels in the blood drop, the parathyroid glands release PTH, which acts on various target organs, including the bones, kidneys, and intestines.

In the bones, PTH stimulates the release of calcium into the bloodstream by promoting the activity of osteoclasts, the cells that break down bone tissue. In the kidneys, PTH increases the reabsorption of calcium, reducing the amount excreted in urine. Additionally, it promotes the activation of vitamin D, which enhances intestinal absorption of calcium from dietary sources. This coordinated action ensures that calcium levels are adequately maintained, which is vital for numerous physiological functions, such as muscle contraction, blood clotting, and nerve function.

The other options do not accurately describe the function of the parathyroid glands, as they pertain to different glands or biological processes entirely. For instance, insulin is secreted by the pancreas to regulate blood sugar, and hormones controlling carbohydrate metabolism are primarily linked to the thyroid and adrenal glands.