Vitamin D metabolism depends on genes that activate vitamin D, transport it, regulate receptor signaling, and break down active metabolites. A DNA file can show variants in these genes, but it does not measure vitamin D level.
Activation enzymes
CYP2R1
CYP2R1 encodes a main hepatic 25-hydroxylase. It converts vitamin D3 to 25-hydroxyvitamin D, the major circulating form measured in many blood tests (R1, R2).
CYP27B1
CYP27B1 performs the next activation step, converting 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D, also called calcitriol. This happens mainly in the kidneys and is regulated by parathyroid hormone, FGF23, and calcitriol itself (R1).
CYP27A1, CYP3A4, CYP2J2, and CYP2J3
These enzymes can contribute to vitamin D hydroxylation in specific tissues or contexts. They are usually reviewed as supporting genes rather than as the core activation pathway.
Breakdown
CYP24A1
CYP24A1 helps break down both 25-hydroxyvitamin D and calcitriol into inactive metabolites. It is part of the feedback system that prevents active vitamin D metabolites from accumulating too much (R1).
Transport
GC
GC encodes vitamin D binding protein. This protein carries vitamin D metabolites in blood and affects how much is bound versus free (R3).
Receptor signaling
VDR and RXR
VDR encodes the vitamin D receptor. When activated by calcitriol, VDR pairs with RXR and helps regulate target genes (R4).
Related regulation
DHCR7
DHCR7 affects availability of 7-dehydrocholesterol, the skin precursor used to make vitamin D after UVB exposure.
FGF23
FGF23 suppresses CYP27B1 and increases CYP24A1 activity in the kidney, reducing calcitriol production (R1).
How to read these genes
Review the gene’s role first: activation, breakdown, transport, receptor signaling, or regulation. Then check variant consequence, frequency, clinical annotations, and whether the finding fits the question. Vitamin D status still needs laboratory testing and clinical context.