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Calcitriol
The hormonally active form of vitamin D, produced by renal CYP27B1-mediated 1α-hydroxylation of 25-hydroxyvitamin D, that binds the nuclear vitamin D receptor (VDR) to regulate calcium and phosphate homeostasis and many noncalcemic gene programs.
Also: 1,25(OH)2D, 1,25-dihydroxyvitamin D
Calcitriol acts on intestine (calcium and phosphate absorption via calbindin, TRPV6, NaPi-IIb), bone (osteoclast differentiation), and parathyroid gland (PTH suppression). Renal production is upregulated by PTH and hypophosphatemia and downregulated by FGF23 and calcitriol itself. Extrarenal CYP27B1 expression in macrophages, skin, and breast underlies the noncalcemic actions emphasized in MNHD's vitamin D chapter.
How one textbook covers it
Modern Nutrition in Health and Disease, 12th ed. — Ch 18: Vitamin D
Calcitriol acts on intestine (calcium and phosphate absorption via calbindin, TRPV6, NaPi-IIb), bone (osteoclast differentiation), and parathyroid gland (PTH suppression). Renal production is upregulated by PTH and hypophosphatemia and downregulated by FGF23 and calcitriol itself. Extrarenal CYP27B1 expression in macrophages, skin, and breast underlies the noncalcemic actions emphasized in MNHD's vitamin D chapter.
Related terms
Calbindin, FGF23, PTH, VDR, Vitamin D