<prompt> Commonest cause of raised serum calcium is -Ecotopic secretionParathyroid hyperplasiaParathyroid adenomaParathyroid carcinoma  <response>: Ans. is c i.e., Parathyroid adenoma o Primary hyperparathyroidism is the most common cause of hypercalcemia overall. o 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 o After hyperparathyroidism, malignancy is the 2nd most common cause of hypercalcemia by one of the following mechanisms. i Osteolysis ii Secretion of parathormone related peptide. 