Parathyroid hormone and electrolytes during long-term treatment with allopurinol and thiazide

We have investigated the composition of plasma and urine in patients with recurrent calcium calculi treated with allopurinol alone, thiazide alone, and both agents together for more than 18 months, and compared the results with those of patients receiving no treatment. In patients treated with allopurinol, both plasma and urinary uric acid were decreased, and plasma parathyroid hormone (PTH) and urinary calcium were increased between 1 and 2 years after treatment. In patients treated with thiazide, plasma calcium was decreased 3 months after treatment but then increased gradually, although the pre-treatment level was not reached. Urinary calcium was decreased 3 months after treatment but returned to pre-treatment levels at 6 and 12 months. Plasma PTH was gradually increased. In patients treated with both allopurinol and thiazide, plasma and urinary uric acid, plasma potassium and urinary calcium were decreased during treatment. Plasma PTH increased gradually during treatment. In patients receiving no treatment, the composition of plasma and urine did not alter during follow-up. The reasons for the changes in urinary calcium and plasma PTH have been discussed.