Leptin is elevated in patients with obesity, but hyperleptinemia in OHS is associated with reduced respiratory drive and blunted hypercapnic response [23] due to central leptin resistance, and it is evident that reduced central chemosensitivity resulting in chronic hypercapnia increases the effects on the respiratory system beyond what we see in patients with eucapnic obesity and eucapnic OSA. Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.