Calcitonin lowers serum calcium acutely by inhibiting osteoclastic resorption, though it plays only a minor role in human calcium homeostasis. From which cells is calcitonin secreted?

• A Parathyroid chief cells
• B Thyroid parafollicular C cells ✓
• C Osteocytes
• D Thyroid follicular epithelial cells

Explanation

Calcitonin is a 32-amino-acid peptide secreted by parafollicular C cells of the thyroid, which derive from the ultimobranchial body of neural crest origin. Its secretion rises with hypercalcemia and it inhibits osteoclast activity, but in humans thyroidectomy without replacement does not derange calcium, showing its minor physiological role. Chief cells make PTH and osteocytes make FGF23 and sclerostin.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.