LEP and diabetes mellitus: The congenital deficit of leptin leads to morbid obesity, severe hyperphagia, hyperinsulinism or type 2 diabetes mellitus, hypogonadotropic hypogonadism, hypofunction of T cells and endocrine/metabolic dysfunctions.15,16 Mutations in the leptin gene are associated with moderate obesity and normal function of the T cells.17 The serum leptin level is dependent on the age and gender, being correlated with the volume of adipose tissue.17–19