Association Between Serum Vitamin D Levels and Insulin Resistance in Women With Polycystic Ovary Syndrome: A Systematic Review and Meta-Analysis.

BACKGROUND

Vitamin D deficiency has been proposed as a potential contributor to insulin resistance (IR) in polycystic ovary syndrome (PCOS); however, the evidence remains inconclusive. This meta-analysis evaluated the association between serum 25-hydroxyvitamin D [25(OH)D] and IR in PCOS.

METHODS

We systematically searched PubMed, Embase, Web of Science, and Cochrane Library up to December 2025 for observational studies reporting correlations of 25(OH)D with IR indices (HOMA-IR/fasting insulin) in women with PCOS. Pooled correlation coefficients (r) with 95% confidence intervals (CI) were calculated using random-effects models.

RESULTS

Fourteen studies involving 1856 women with PCOS were included. A significant inverse correlation was found between serum 25(OH)D and IR (pooled r = -0.32, 95% CI: -0.40 to -0.23; p < 0.001; I2 = 58%). Subgroup analyses revealed stronger associations in overweight/obese women (r = -0.35) and in Asian populations (r = -0.36). Women with vitamin D deficiency (< 20 ng/mL) showed a stronger correlation (r = -0.38). Sensitivity analysis confirmed robustness, and no significant publication bias was detected.

CONCLUSION

Lower serum vitamin D is significantly associated with greater insulin resistance in PCOS, especially in overweight/obese and Asian subgroups. These findings highlight the potential value of assessing vitamin D status in the metabolic evaluation of PCOS.