What is the main function of parathyroid hormone?

• A. To decrease blood sugar levels
• B. To increase blood calcium levels
• C. To stimulate metabolism
• D. To facilitate fat storage

Answer: (B)

Parathyroid hormone (PTH) plays a critical role in regulating calcium levels in the blood. Its primary function is to increase blood calcium levels when they drop below a certain threshold. It achieves this by acting on several organs: it stimulates the release of calcium from bones, increases the reabsorption of calcium in the kidneys, and enhances the activation of vitamin D in the kidneys, which in turn promotes the absorption of calcium from the intestines.

This hormonal regulation is vital because calcium is essential for many bodily functions, including muscle contraction, nerve function, and blood clotting. When calcium levels are low, PTH helps to restore balance by ensuring that enough calcium is available for these critical processes. Therefore, the primary function of parathyroid hormone is to increase blood calcium levels, making this the correct answer.