Primary hyperparathyroidism.

Hyperparathyroidism was described initially in the mid 1920s in patients suffering from a rare and severe form of bone disease, osteitis fibrosa cystica. In the 1940s and 1950s renal stone disease was recognized as a far more frequent complication of primary hyperparathyroidism than bone disease, and approximately half of the patients with primary hyperparathyroidism in clinical series published through the 1970s presented with renal stones. The introduction of routine determination of serum calcium concentration in the mid 1970s has had a dramatic impact on the frequency with which primary hyperparathyroidism is diagnosed in the population, particularly in older individuals with predominantly nonspecific symptoms of the disease. Stone complications appear to occur in less than 10 per cent of such patients. Underlying primary hyperparathyroidism is diagnosed in approximately 1 to 5 per cent of the patients with calcium stone disease. The predominant risk factor for stone formation in primary hyperparathyroidism is hypercalciuria, and patients typically present with moderate to marked hypercalciuria but with only mild hypercalcemia, in the range of 11 mg. per dl. or less. Hypercalciuria in these patients is principally the result of 1,25-dihydroxyvitamin D-mediated hyperabsorption of calcium from the intestine. The pattern of hypercalciuria disproportionate to the degree of hypercalcemia that typifies patients with primary hyperparathyroidism and stone disease reaches an extreme degree in patients with so-called subtle or normocalcemic primary hyperparathyroidism, in whom diagnosis by routine techniques may be difficult. Parathyroid exploration remains the treatment of choice in patients with primary hyperparathyroidism and stone complications.