PTH and neoplasm: It has been proposed that the abnormalities in bone and mineral metabolism may be caused by direct invasion of the cells of the bone and bone marrow microenvironment, chronic T-cell activation and abnormal cytokine production affecting osteoblast and osteoclastic functions, disturbances of calcium homeostasis, parathyroid hormone functions, vitamin D metabolism, opportunistic or neoplastic disease and adverse effects of drugs[12].