IGF1 and obesity due to melanocortin 4 receptor deficiency: In addition, a compensatory increase in SST levels (circulating and stomach mRNA) observed in CORT-KO mice [50] could provide an explanation to why the obesity-induced up-regulation of GH/IGF-I system is completely blunted only in CORT-KO, since it has been previously reported that SST can directly decrease the expression of GH-R, IGF-I and IGFI-R in a variety of tissues [66–68].