Journal
JOURNAL OF STEROID BIOCHEMISTRY AND MOLECULAR BIOLOGY
Volume 165, Issue -, Pages 101-108Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jsbmb.2016.04.001
Keywords
Calcium; CYP2R1; CYP27B1; CYP24A1; Neonatal hypercalcemia; Rickets; Secosteroid
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Vitamin D, an inactive secosteroid pro-hormone, is produced by the action of ultraviolet light on 7-dehydrocholesterol in the skin. The active hormone, 1,25(OH)(2)D is produced by sequential 25-hydroxylation in the liver, principally by CYP2R1, and 1 alpha-hydroxylation in the kidney by CYP27B1. Mutations in CYP27B1 cause la-hydroxylase deficiency, also known as vitamin D dependent rickets type I or hereditary pseudo-vitamin D deficient rickets; very rare mutations in CYP2R1 can cause 25-hydroxylase deficiency. Both deficiencies cause hypocalcemia, secondary hyperparathyroidism, severe rickets in infancy, and low serum concentrations of 1,25(OH)(2)D; both disorders respond to hormonal replacement therapy with calcitriol. The inactivation of vitamin D is principally initiated by its 23- and 24-hydroxylation by CYP24A1. Mutations in CYP24A1 can cause both severe neonatal hypercalcemia and a less severe adult hypercalcemic syndrome. Other pathways of vitamin D metabolism are under investigation, notably its 20-hydroxylation by the cholesterol side-chain cleavage enzyme, CYP11A1. (C) 2016 Elsevier Ltd. All rights reserved.
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