PTH and hypercalcemia disease: The most common causes of hypercalcemia are malignancy and hyperparathyroidism (HPT).1,2 There are 4 mechanisms of malignancy-related hypercalcemia, including humoral hypercalcemia via the secretion of parathyroid hormone-related peptide (PTHrP), local osteolytic hypercalcemia, excess production of extra-renal 1,25-dihydroxyvitamin D, and ectopic secretion of parathyroid hormone.3 The primary goal of therapy is the treatment of the underlying malignancy.