Question

Parathormone influences calcium absorption in the small intestine by regulating the metabolism of:

• A. Vitamin B6
• B. Vitamin D
• C. Vitamin C
• D. Enterogastrone

Answer 1

The correct option is B Vitamin D

The parathyroid glands secrete a peptide hormone called parathyroid hormone (PTH). The secretion of PTH is regulated by the circulating levels of calcium ions.
PTH is a hypercalcemic hormone. It increases calcium absorption in small intestine by regulating metabolism of vitamin D by stimulating osteoclasts. These are the cells that cause breakdown by dissolution of calcium from bone and thus, concentration of calcium is increased in blood. Therefore, PTH increases $C{a}^{2+}$ levels in the blood, absorption in the bone and increases its absorption in digested food.