INS and obesity due to melanocortin 4 receptor deficiency: Although MHO phenotype was first described during the early 1980s, and is frequently defined (on the basis of known metabolic abnormalities associated with obesity) by the absence of MS components and/or preserved insulin sensitivity, a consensus-based definition of pediatric MHO was introduced only recently, in 2018 (4, 7, 13, 19, 20).