Calcitriol
Calcitriol, a vitamin. The fully activated vitamin D hormone — formed by renal CYP27B1 1α-hydroxylation of calcifediol. Binds VDR with ~1000× higher affinity than the…
The fully activated vitamin D hormone — formed by renal CYP27B1 1α-hydroxylation of calcifediol. Binds VDR with ~1000× higher affinity than the precursors; drives the classical genomic actions (intestinal Ca²⁺/P absorption via TRPV6/calbindin, bone remodelling, PTH suppression). Narrow therapeutic window — skips all regulatory hydroxylation, so hypercalcemia and soft-tissue calcification are dose-limiting. Used clinically when the kidney cannot perform the 1α-hydroxylation step (CKD stage 4–5).
Related compounds
- Vitamin D3 — caution
- Calcium — caution
- Magnesium — synergistic
Sources: PMID:8704116, PMID:19427587