PTH and hypercalcemia disease: Four mechanisms of hypercalcemia in malignancy have been described: local osteolysis, parathyroid hormone related-protein (PTHrP) mediated, 1,25-dihydroxyvitamin D (1,25(OH)2D3, calcitriol) secretion, and ectopic parathyroid hormone (PTH) [4,5].