Bone loss results from low body fat mass and a decreased energy intake resulting in hypothalamic amenorrhea and hypogonadism with complex neuroendocrine hormone dysregulation (such as increases in ghrelin, cortisol, PYY and growth hormone (GH) with GH resistance, and decreases in levels of insulin, IGF1 and oxytocin) and changes in levels of adipokines (low leptin and high adiponectin levels) [26]. The gene discussed is GH1; the disease is hypogonadism.