In summary, taking all these observations into account our findings suggest that the increased leptin levels described so far in patients with OSA is mostly associated with obesity and not with the disease itself or its severity; accordingly short and long term treatment with CPAP has a small effect on leptin plasma levels and Auto-CPAP therapy compliance is not related with the leptin values decrease. Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.