Among the numerous factors that could influence the timing and tempo of pubertal development are foetal nutrition, birth weight, childhood dietary habits, physical activity, psychological factors, exposure to electromagnetic fields (EMF) and/or endocrine disrupting, the activating effect of leptin on GnRH—gonadotropin axis and hyperinsulinemia related to obesity [21]. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.