The parathyroid hormone is secreted by which gland?

• A. Thyroid gland
• B. Parathyroid gland
• C. Adrenal gland
• D. Pituitary gland

Answer: (B)

PTH secretion is the job of the parathyroid glands. These small glands sit on the back of the thyroid and release parathyroid hormone to raise blood calcium when levels drop. It does this by stimulating bone breakdown to release calcium, increasing calcium reabsorption in the kidneys, and promoting production of active vitamin D to boost intestinal calcium absorption. This hormone is part of a negative feedback loop—when calcium is high, PTH release decreases. The thyroid gland makes thyroid hormones and calcitonin (which tends to lower calcium), the adrenal gland produces steroids and catecholamines, and the pituitary gland releases other endocrine hormones; none of these secrete parathyroid hormone.