In order to elucidate the influence of the parathyroid function on the uric acid metabolism, 24 patients (14 males, 10 females) with primary hyperparathyroidism (PHP) and 17 patients (9 males, 8 females) with idiopathic hypoparathyroidism (IHP) were extensively studied. The mean age was not significantly different between these groups, being 40.3 +/- 2.8 and 39.0 +/- 3.5 respectively. Hyperuricemia was found in 4 patients with PHP, but none of the patients had experienced gout. The serum uric acid levels were significantly higher and uric acid clearances were significantly lower in PHP than in IHP. There was no difference in daily urinary excretion of uric acid and in creatinine clearance between the two groups. In PHP, a positive correlation was observed between the levels of serum uric acid and calcium, both of which negatively correlated to renal uric acid clearance. Although the serum uric acid levels did not correlate to serum PTH levels in PHP, the removal of parathyroid adenoma resulted in a significant fall of serum uric acid levels. In IHP, the administration of PTH induced a small but significant decrease in serum uric acid levels with a coincidental increase in urinary uric acid excretion. Four hours of calcium infusion had no effect on the serum uric acid levels and urinary uric acid excretion. Treatment of IHP with 1 alpha-OH D3 to restore normal serum calcium levels caused significant increase in serum uric acid levels. These data indicate that the parathyroid function influences uric acid metabolism, even in the absence of renal insufficiency, mainly through changes of uric acid clearance. Levels of active vitamin D or chronically abnormal calcium levels in the circulation may be major determinant for uric acid metabolism in parathyroid disorders.