To accomplish this, an extensive search in PubMed, Embase, and Cochrane Library was performed by two independent authors using the following key-words: “osteoporosis”, “bone mineral density”, “Thyroid-stimulating hormone (TSH)”, “cortisol”, “estradiol”, “testosterone”, “follicle-stimulating hormone (FSH)”, “luteinizing-hormone (LH)”, parathyroid hormone”, “vitamin D”, and “Insulin-like growth factor 1 (IGF1)”. The gene discussed is IGF1; the disease is osteoporosis.