Which hormone is responsible for producing 1,25-dihydroxyvitamin D in the kidney?

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Multiple Choice

Which hormone is responsible for producing 1,25-dihydroxyvitamin D in the kidney?

Explanation:
PTH drives the kidney to activate vitamin D. It stimulates the enzyme 1-alpha-hydroxylase in proximal tubule cells, converting 25-hydroxyvitamin D into 1,25-dihydroxyvitamin D (calcitriol), the active form. Calcitriol then increases intestinal absorption of calcium and phosphate, helping raise and maintain serum calcium. This hormonal axis is why PTH, not TSH, ACTH, or CRH, is the key regulator of renal vitamin D activation. The rise in calcium from calcitriol and PTH feeds back to reduce PTH release, completing the loop.

PTH drives the kidney to activate vitamin D. It stimulates the enzyme 1-alpha-hydroxylase in proximal tubule cells, converting 25-hydroxyvitamin D into 1,25-dihydroxyvitamin D (calcitriol), the active form. Calcitriol then increases intestinal absorption of calcium and phosphate, helping raise and maintain serum calcium. This hormonal axis is why PTH, not TSH, ACTH, or CRH, is the key regulator of renal vitamin D activation. The rise in calcium from calcitriol and PTH feeds back to reduce PTH release, completing the loop.

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