25-hydroxyvitamin D is key in maintaining Calcium homeostasis, by promoting Calcium intestinal absorption. Can hypercalcemia (for instance secondary to a primary hyperparathyroidism) cause a retroactive inhibition of enzymes located in the 25-hydroxyvitamin D production (such as cholecalciferol 25-hydroxylase)?
Thank you for your answers.
some of my patients with hypercalcemia have normal 25-hydroxyvitamin D levels, Therefore I don't think that it is inhibited.
25-hydroxylation, the first step in vitamin D metabolism, does not appear to be under negative feedback and is poorly regulated. In particular, it is not regulated by calcemia or calcium intake in contrast to renal 1a-hydroxylation.
Henry HL. Regulation of vitamin D metabolism. Best Pract Res Clin Endocrinol Metab 2011;25:531-41.
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