IGF1 and Prader-Willi syndrome: Since individuals with PWS have short stature after early childhood that is in part due to growth hormone (GH) deficiency, and the growth retardation of Snord116del mice persisted to adulthood, we measured the direct downstream effector of GH action, the transcript levels of insulin-like growth factor (Igf1, GeneID: 16000) in liver.