INS and obesity due to melanocortin 4 receptor deficiency: We performed tests for trends in subgroups based on BMI, and found that, in the obesity group, serum TSK level was associated with BMI (β ± SE: 0.63 ± 0.31, P = 0.049), VFA (β ± SE: 12.15 ± 5.94, P = 0.011), 30-min insulin after OGTT (β ± SE: 11.70 ± 5.82, P = 0.045), 2-h insulin after OGTT (β ± SE: 21.14 ± 8.02, P = 0.009), and homeostatic model assessment for insulin resistance (HOMA-IR) index (β ± SE: 3.57 ± 1.61, P = 0.027) (Table 2 and Fig. 1b–g).