Sex differences in uric acid metabolism in adults: evidence for a lack of influence of estradiol-17 beta (E2) on the renal handling of urate.

The serum urate concentration of adult women, which is lower than in men of a similar age, is thought to be related to a higher renal clearance of urate in women, possibly due to their higher plasma estrogen levels. Intersexual differences in the renal handling of uric acid was assessed in 9 normal adult women and 9 normal age-matched men. Women showed a significantly lower serum urate concentration as compared to men (3.5 +/- 0.3 v 4.9 +/- 0.7 mg/dL, P less than 0.001), higher fractional excretion of urate (9.8 +/- 1.0 v 7.3 +/- 0.8%, P less than 0.001), and significantly lower tubular urate postsecretory reabsorption (67.2 +/- 1.6 v 76.6 +/- 1.4% of secreted urate, P less than 0.01). To test whether plasma E2 has a uricosuric effect we administered estradiol valerate and estradiol benzoate to either oophorectomized or adult women. Plasma E2 levels and urinary total estrogen excretion increased significantly in both groups but the treatment failed to significantly modify serum urate or the fractional excretion of uric acid. Furthermore, in 4 normal adult women, the tubular phases that modulate the renal excretion of urate were not significantly influenced by increased plasma E2 levels. We conclude that in comparison to men of a similar age, the lower tubular urate postsecretory reabsorption of adult women is in accordance with the intersexual differences in uric acid metabolism. Plasma E2 does not influence renal handling of uric acid or serum urate levels.