Medicine Endocrinology e6dbd902 The commonest cause of primary hyperparathyroidism is- A Carcinoma parathyroid B Solitary adenoma of parathyroid C Chronic renal failure D Hyperplasia of the parathyroid High-Yield Explanation solitary adenoma ie a single abnormal gland is the cause in 80% of patients ( Harrison 17 pg 2380)