Although no evidence of osteosarcoma has been observed in humans treated with PTH (18, 58), PTH should be avoided in patients with elevated risk of osteosarcoma and a history of cancer, including adolescents in whom the epiphyses have not yet closed, those with Paget’s disease or prior skeletal radiation, and patients with unexplained increases in alkaline phosphatase (59). The gene discussed is PTH; the disease is Paget disease.