HYPERPARATHYROIDISM DURING LITHIUM-THERAPY - 2 NEW CASES

We report two new cases of hyperparathyroidism during lithium therapy. The patients were a 50-year-old male and a 48-year-old female under l ithium for bipolar disease. Both developed osteoporosis without fractu res and laboratory test abnormalities consistent with moderate hyperpa rathyroidism. Although only 30 or so cases of lithium-associated hyper parathyroidism have been reported, as many as 10 to 15% of lithium-tre ated patients may have laboratory test evidence of hyperparathyroidism . Typically, urinary calcium excretion is normal, serum phosphate leve ls are moderately decreased and cyclic AMP levels are normal. An adeno ma is the most common lesion. Surgery is usually required in patients whose clinical and laboratory test abnormalities persist despite disco ntinuation of the drug. Lithium-associated hyperparathyroidism may be due to dysregulation of the caliostat, a feedback loop that subordinat es parathyroid hormone secretion to serum calcium levels. Little is kn own about lithium-induced osteoporosis. Trabecular bone was predominan tly affected in one of our patients and cortical bone in another.