Several lines of evidence suggest the role of leptin in the pathogenesis of arterial hypertension: (1) chronic leptin administration [6] or transgenic overexpression [7] increases blood pressure (BP) in experimental animals, (2) BP is not increased in leptin-deficient ob/ob mice despite severe obesity, and supplementation of leptin to these animals increases BP despite reducing body weight [8], (3) some studies indicate that plasma leptin concentration is higher in patients with arterial hypertension independently of body weight [9]. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.