Hyperuricemia, low urine urate excretion and target organ damage in arterial hypertension.

Background: Hyperuricemia can be the consequence of an increased urate production, a decreased renal excretion, or both. An increased prevalence of hyperuricemia has been described in essential hypertensive patients partly due to a decreased renal urinary urate excretion (UUE). Hyperuricemia has been shown to be associated with an increased risk of cardiovascular disease in hypertensive patients in some but not in all epidemiological studies in which this relationship has been investigated. Objective: To assess the influence of low UUE in the association between serum urate, renal function and hypertension severity. Patients and Methods: This cross-sectional study was carried out in a sample of 677 male hypertensive patients, aged 35-60 years, with essential arterial hypertension consecutively attended in a hospital hypertension unit. The presence of hypertension-related organ damage at diagnosis was classified according to classical WHO criteria as grade 1, 2 or 3. Urate underexcretion was defined as 24-h urinary urate below the product serum urate x 100. Results: Mean serum urate levels were 6.4 +/- 1.6 mg/dl in the total sample. Hyperuricemia (serum urate >7 mg/dl) was present in 28.5% of patients and only 17.0% had underexcretory hyperuricemia. This subgroup of patients exhibited the higher rate of hypertension-related target organ damage (TOD). A multivariate analysis, showed that underexcretory hyperuricemia but not hyperuricemia remained an independent predictor of TOD (odds ratio 2.5. 95% CI 1.6-3.89). Serum urate correlated positively with serum creatinine in hyperuricemic patients ( r = 0.50, p < 0.001), but not in patients with underexcretory hyperuricemia ( r = 0.21, p = 0.18). Conclusions: Underexcretory hyper-uricemia is strongly related to hypertensive organ damage and this relationship does not seem to be mediated by a decreased renal function. This aspect could underline the predictive value of hyperuricemia independently of serum creatinine. UUE could improve the clinical predictive value of hyperuricemia as a cardiovascular risk factor.