Normocalcemic primary hyperparathyroidism

In recent years it has become recognized that patients with primary hyperparathyroidism, particularly those with renal stones, may present with serum calcium concentrations that are within the normal range. The three patients described herein all presented with a long history of recurrent renal calculi, normal serum calcium and phosphorus concentrations, and hypercalciuria while taking an unregulated diet. In all three patients, the diagnosis of primary hyperparathyroidism was proved by surgical exploration of the neck and biopsy of all four parathyroid glands. In two, a parathyroid adenoma was found; in the third, parathyroid hyperplasia. The disease in these three patients was classified as normocalcemic primary hyperparathyroidism.