IGF1 and obesity due to melanocortin 4 receptor deficiency: Our findings are in marked contrast to those reported in children with idiopathic, hyperleptinemic obesity who usually have normal [17–19], or increased [20, 21] IGF1 serum levels, whereas weight loss in these children is typically associated with either a decrease [20, 36] or no change in IGF1 levels [37, 38].