HYPERURICEMIA IN PATIENTS WITH HYPERTHYROIDISM DUE TO GRAVES-DISEASE

The effects of hyperthyroidism on uric acid metabolism were investigated. First, the serum uric acid level was measured in 92 patients with hyperthyroidism due to Graves' disease, eight patients with subacute thyroiditis, six patients with hypothyroidism, and 70 sex- and age matched controls. Second, the correlation between serum thyroxine (T-4) and serum uric acid was obtained in hyperthyroid Graves' disease patients before and during antithyroid drug therapy. Finally, uric acid clearance (C-UA) was determined in untreated patients with hyperthyroidism due to Graves' disease. Serum uric acid was significantly elevated in patients with hyperthyroidism, and the elevation correlated well with serum T-4 before treatment as a group and during treatment in each patient. A significant elevation of serum uric acid was not present in patients with a transient mild thyrotoxicosis due to subacute thyroiditis. Serum uric acid was significantly decreased in patients with hypothyroidism. Renal excretion of uric acid clearly increased in hyperthyroid patients, and C-UA also increased. The increase in C-UA corresponded to the increase in renal plasma flow (RPF), which was measured by p-aminohippuric acid clearance. The fractional excretion of uric acid as determined by C-UA/glomerular filtration rate (GFR) was similar and within the normal range in hyperthyroid patients and normal controls. A significant inverse correlation between C-UA and serum uric acid concentration was present in hyperthyroid patients as in normal controls, indicating that the renal handling of uric acid in the tubule affected uric acid excretion. However, the regression line of the correlation between C-UA and serum uric acid in hyperthyroid patients was steeper than that in controls, with the contiguous intercept on the abscissa. We conclude that the serum uric acid concentration increased in hyperthyroidism due to an increased production that surmounted the increase in C-UA. Copyright (C) 1995 by W.B. Saunders Company