Objective: The relationship between fertilization rates and
1,25-dihydroxyvitamin D (
1,25(OH)2D3),
25-hydroxyvitamin D2 (25(
OH)D2),
25-hydroxyvitamin D3 (25(
OH)D3),
24,25-dihydroxyvitamin D (24,25(
OH)2D3), and 25-hydroxy-3epi-Vitamin D3 (3epi25(
OH)D3) concentrations in age and weight matched women with and without PCOS was studied. Methods: Fifty nine non-obese women, 29 with PCOS, and 30 non-PCOS undergoing IVF, matched for age and weight were included. Serum
vitamin D metabolites were taken the menstrual cycle prior to commencing controlled ovarian hyperstimulation. Results:
Vitamin D metabolites did not differ between PCOS and controls; however, 25(
OH)D3 correlated with embryo fertilization rates in PCOS patients alone (p = 0.03). For all subjects, 3epi25(
OH)D3 correlated with fertilization rate (p < 0.04) and negatively with HOMA-IR (p < 0.02); 25(
OH)D2 correlated with cleavage rate, G3D3 and blastocyst (p < 0.05; p < 0.009; p < 0.002, respectively). 24,25(
OH)2D3 correlated with AMH,
antral follicle count, eggs retrieved and top quality embryos (G3D3) (p < 0.03; p < 0.003; p < 0.009; p < 0.002, respectively), and negatively with HOMA-IR (p < 0.01).
1,25(OH)2D3 did not correlate with any of the metabolic or embryo parameters. In slim PCOS, 25(
OH)D3 correlated with increased fertilization rates in PCOS, but other
vitamin D parameters did not differ to matched controls. Conclusion: 3epi25(
OH)D3, 25(
OH)D2, and 24,25(
OH)2D3, but not
1,25(OH)2D3, were associated with embryo parameters suggesting that
vitamin D metabolites other than
1,25(OH)2D3 are important in fertility.