<prompt> Most common cause of hyperparathyroidism: March 2009CarcinomaHyperplasiaAdenomaFamilial isolated hyperparathyroidism  <response>: Ans. C: Adenoma Hyperparathyroidism causes hypercalcemia through the excessive secretion of parathyroid hormone, usually by an adenoma benign tumors of the parathyroid glands nearly 80. Chief cell parathyroid hyperplasia accounts for nearly 15 cases. 