Although obesity is responsible of functional hypogonadotropic hypogonadism, a decrease of serum T levels is predictive of metabolic syndrome, unfavorable changes of body composition (increase of fat mass and decrease of fat free mass), lower insulin sensitivity, higher waist circumference, fasting glucose, triglyceride, and LDL-cholesterol levels at all ages [75]. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.