The commonest cause of raised serum calcium is -

Primary hyperparathyroidism is the most common cause of hypercalcemia overall. The frequency of the various parathyroid lesions underlying the hyperfunction is as follows : - Parathyroid adenoma - 75% to 80% Primary hyperplasia - 10% to 15% ​Parathyroid carcinoma- < 5% After hyperparathyroidism, malignancy is the 2nd most common cause of hypercalcemia by one of the following mechanisms. Osteolysis Secretion of parathormone related peptide.