PTH and primary hyperparathyroidism: Primary hyperparathyroidism (PHPT) is a common endocrine disorder of calcium metabolism characterized by hypercalcemia and elevated or inappropriately normal concentrations of parathyroid hormone (PTH) [1] due to a benign overgrowth of parathyroid tissue either as a single-gland (80% of cases) or as a multiple-gland disorder (15–20% of cases).