The BDNF/leptin quotient was lowest in PWS patients (PWS: 3.9 (1.6–8.8) vs Obese: 11.1 (5.5–25.9) vs Lean: 35.3 (19.6–76.8); Χ2 = 44.79, p<0.001). The gene discussed is BDNF; the disease is Prader-Willi syndrome.