Calcitriol increases intestinal calcium absorption by inducing synthesis of which protein in the enterocyte?
- A Fibroblast growth factor 23
- B Osteocalcin
- C Calbindin ✓
- D Parathyroid hormone-related peptide
Correct answer: C. Calbindin
Explanation
Calcitriol binds the nuclear vitamin D receptor in enterocytes and upregulates calbindin (calcium-binding protein), TRPV6 channels, and brush border ATP-dependent calcium pumps, raising calcium uptake. Osteocalcin (option B) is a vitamin K-dependent osteoblast protein, and FGF23 (option A) is produced by osteocytes to suppress calcitriol, so neither mediates intestinal absorption.
Reference: Williams Textbook of Endocrinology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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