Adjusting the influence of confounders including obesity (BMI, WHR, WC and HC) and IR (represented by fasting insulin) in mvMR analysis, we found that it was disappeared for the causal relationship between genetically predicted PCOS and 25OHD (P > 0.05) (Figure 3; Supplemental Material S4). Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.