Previous studies have demonstrated that the regulation of leptin and T levels seems to be bidirectional.28,29 Our population level study supports previous findings in smaller sample size studies that establish negative associations between leptin and serum T28 and a positive association between leptin and obesity.7,8 The presence of a significant association between leptin and T independent of waist circumference indicates that elevated leptin levels could lead to TD regardless of body composition. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.