SLC6A4 and obesity due to melanocortin 4 receptor deficiency: In lean men, hypothalamic SERT availability significantly increased by 48.3% ± 76.4% (p = 0.044) upon 24 h of fasting, which is in contrast to the unchanged hypothalamic SERT availability (−36.3% ± 71.1%, p = 0.179) in men with obesity (Table 2).