ANSWER: (A) AdenomaREF: Blueprints Surgery by Seth J. Karp, James Morris, David I. Soybel Page 85Hyperparathyroidism is the most common cause of surgically correctable hypercalcemia.Primary hyperparathyroidism is a surgical disease and operation is required for the hyperfunctioning gland (A single hyperfunctioning adenoma accounts for approximately 90% cases)Secondary hyperparathyroidism of renal disease is treated medically.Tertiary hyperparathyroidism due to autonomous parathyroid hyperplasia occasionally requires surgery.