Home Sim1 haploinsufficiency causes hyperphagia, obesity and reduction of the paraventricular nucleus of the hypothalamus. Sim1 haploinsufficiency causes hyperphagia, obesity and reduction of the paraventricular nucleus of the hypothalamus. Michaud, JL; Boucher, F; Melnyk, A; Gauthier, F; Goshu, E; Levy, E; Mitchell, GA; Himms-Hagen, J; Fan, CM 2001 AMERICAN JOURNAL OF HUMAN GENETICS