Several factors play a causal role in this growth retardation, including small infant size at birth, metabolic acidosis, salt and water deficits, anorexia, malnutrition and cachexia, anemia, and resistance to anabolic hormones such as growth hormone (GH), insulin-like growth factor 1 (IGF1), and sexual hormones. This evidence concerns the gene IGF1 and Anorexia.