25-Hydroxyvitamin D
The major circulating form of vitamin D and the standard biomarker of vitamin D status, produced by hepatic CYP2R1-mediated 25-hydroxylation of vitamins D2 and D3.
Also: 25(OH)D, Calcidiol
Serum 25(OH)D integrates cutaneous synthesis and dietary intake and has a half-life of about three weeks. MNHD discusses thresholds: <30 nmol/L (12 ng/mL) defines deficiency for bone health under IOM criteria, 50 nmol/L (20 ng/mL) is sufficiency for most, while the Endocrine Society proposes higher targets. Active 1,25(OH)2D is not a status biomarker because secondary hyperparathyroidism can keep it normal even in deficiency.
How one textbook covers it
Modern Nutrition in Health and Disease, 12th ed. — Ch 18: Vitamin D
Serum 25(OH)D integrates cutaneous synthesis and dietary intake and has a half-life of about three weeks. MNHD discusses thresholds: <30 nmol/L (12 ng/mL) defines deficiency for bone health under IOM criteria, 50 nmol/L (20 ng/mL) is sufficiency for most, while the Endocrine Society proposes higher targets. Active 1,25(OH)2D is not a status biomarker because secondary hyperparathyroidism can keep it normal even in deficiency.
Related terms
Calcitriol, PTH, Vitamin D