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. 2022 Jan 9;14(2):269. doi: 10.3390/nu14020269

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© 2022 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Vitamin D is synthesized in the skin in response to ultraviolet light or provided by the diet. It is first converted to 25-hydroxyvitamin D3 by hydroxylation occurring in the liver and then further converted into its active metabolite, 1,25-dihydroxyvitamin D3, in the kidney. Ca = calcium; P = phosphate; CYP2R1 = Cytochrome P450 Family 2 Subfamily R Member 1; CYP27B1= Cytochrome P450 Family 27 Subfamily B Member 1; 25(OH) vitamin D = 25-hydroxyvitamin D; 1,25 (OH) Vitamin D = 1,25-dihydroxyvitamin D.