Which cell type secretes calcitonin, and what is its primary physiologic action?

• A Parafollicular C cells of the thyroid; increases renal calcium reabsorption
• B Chief cells of the parathyroid; stimulates osteoblastic bone formation
• C Parafollicular C cells of the thyroid; inhibits osteoclastic bone resorption ✓
• D Follicular epithelial cells of the thyroid; inhibits osteoclastic bone resorption

Explanation

Calcitonin is produced by the parafollicular A cells, which lie between thyroid follicles and arise from neural crest tissue. Its main action is to inhibit osteoclast activity and reduce bone resorption, lowering serum calcium modestly. It does not act on renal calcium handling as its primary effect. Follicular epithelial cells produce T3 and T4, not calcitonin, so option D fails on cell identity despite the correct action.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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