Vitamin D metabolism

"Vitamin D metabolism" refers not to a single molecule or receptor but rather the complex biochemical pathway by which inactive forms of vitamin D—cholecalciferol (vitamin D3) from skin synthesis/diet and ergocalciferol (vitamin D2) from diet—are converted into their biologically active forms. This process involves two key hydroxylation steps: first in the liver by enzymes such as CYP2R1 producing 25-hydroxyvitamin D [calcidiol], then primarily in the kidney by CYP27B1 yielding 1α,25-dihydroxyvitamin D [calcitriol], which is the hormonally active form. Calcitriol exerts its effects mainly through binding to the nuclear vitamin D receptor (VDR), regulating gene transcription related to calcium/phosphate homeostasis and other cellular processes. Catabolism occurs via further hydroxylation by enzymes like CYP24A1 leading ultimately to inactive metabolites[3][4][7]. Note: "Vitamin D metabolism" is not itself a therapeutic target such as an enzyme or receptor; it describes an entire metabolic pathway involving multiple enzymes and receptors. The main druggable targets within this pathway are specific enzymes like CYP27B1 or receptors like VDR—not “metabolism” per se. Therefore, this entry should be flagged as incorrect for use as a canonical drug target name. Summary of issues: The term “Vitamin D metabolism” does not refer specifically enough to any single molecular entity that can serve directly as a therapeutic target; it encompasses several molecules including enzymes and receptors involved in processing vitamin D compounds[4]. For structured data purposes you should instead specify individual components such as “Vitamin D receptor” (VDR) or relevant metabolic enzymes (CYP27B1, CYP24A1, etc.).

Not applicable to "Vitamin D metabolism" as a target, but for drugs affecting this pathway: Drugs such as cholecalciferol and ergocalciferol are converted in the liver to 25-hydroxyvitamin D, then in the kidney to 1,25-dihydroxyvitamin D. The active metabolite binds to the vitamin D receptor, modulating gene expression involved in calcium/phosphate absorption and bone health[1][3][5].