PLAB Endocrinology Practice Exam

Parathyroid hormone (PTH) is the hormone responsible for increasing blood calcium levels. It is secreted by the parathyroid glands in response to low blood calcium concentrations. PTH increases calcium levels through several mechanisms: it stimulates the release of calcium from bones, enhances the reabsorption of calcium in the kidneys, and promotes the activation of vitamin D in the kidneys, which in turn increases intestinal absorption of calcium.

This coordinated response ensures that when calcium levels in the blood drop, PTH acts quickly to restore them to normal levels. The other hormones mentioned play different roles in the body; for example, calcitonin works to lower blood calcium levels, while insulin is primarily involved in glucose metabolism, and growth hormone influences overall growth and metabolism but does not directly regulate calcium levels in the same way as PTH.