The maturation of the endocrine pancreas continues for several weeks postnatally, with a continuous increase in population size and discrete phases of renewed acceleration in growth activities, especially for beta cells.33 Studying the impact of obesity during this period of intense pancreatic development is therefore particularly relevant.33 We used a mouse model of early induction of obesity31 to characterize PINS plasticity and its functional consequences. The gene discussed is GPSM2; the disease is obesity due to melanocortin 4 receptor deficiency.