IGF1 and obesity due to melanocortin 4 receptor deficiency: Some hormonal and metabolic alterations that occur in obesity, such as decreased testosterone, may decrease prostate cancer risk; however, other alterations such as high insulin, insulin-like growth factor 1 (IGF-1) and/or leptin levels (Frystyk et al, 1995) have mitogenic effects (McKeehan et al, 1984) and can potentially increase risk by promoting prostate cancer progression (Yu and Rohan, 2000; Chan et al, 2002; Jenks, 2010).