Results showed that the causal effect of serum SHBG levels on lower extremity varicose veins risk was retained (OR=1.50; 95% CI:1.13-1.99; P=5.61×10-3), indicating that serum SHBG levels had an independent causal effect on lower extremity varicose veins risk. Here, SHBG is linked to Varicose veins.