JAK2 and obesity due to melanocortin 4 receptor deficiency: Mice with a STAT5 deletion in the brain causes hyperphagia and obesity, whereas activation of STAT5 in hypothalamic neurons inhibits food intake [32], but less severely than in mice with a STAT3 deletion, suggesting that the JAK2/STAT5 signaling plays a minor role in leptin’s regulation of feeding and body weight [33].