Most common cause of primary hyperparathyroidism-: (A) Iatrogenic, (B) Medullary carcinoma thyroid, (C) Parathyroid adenoma, (D) Parathyroid hyperplasia
Answer is C. Most common cause of primary hyperparathyroidism is autonomous secretion of parathyroid hormone (PTH) by a parathyroid adenoma. Single adenoma (90%), multiple adenomas(4%), nodular hyperplasia(5%), carcinoma(1%). Reference : page 769 Davidson's Principles and practice of Medicine 22nd edition