POMC and obesity due to melanocortin 4 receptor deficiency: The authors set out to explore the molecular mechanism behind late-onset obesity in androgen receptor knock-out (ARKO) mice, which they suggest is caused by a hyper-corticoid state, driven by high levels of pituitary-derived ACTH as a consequence of impairment in the hypothalamic-pituitary-adrenal (HPA) axis.