Hyperuricemia in childhood primary hypertension

Abstract

Experimental animal models suggest that uric acid might have a pathogenic role in the early development of primary hypertension. We hypothesized that serum uric acid is correlated with blood pressure in children with new-onset, untreated, primary hypertension. We evaluated 125 consecutive children referred to the Baylor Pediatric Renal Program for evaluation of hypertension. None of the subjects had previously been evaluated or treated for hypertension. The children ranged in age from 6 to 18 years (mean, 13.4+/-3.3) and had normal renal function (creatinine clearance >80 mL x min(-1) x 1.73 m(-2)). Sixty-three children had primary hypertension, 40 had secondary hypertension, and 22 had white-coat hypertension. Forty controls with normal blood pressure were recruited from the renal clinic. Uric acid levels were directly correlated with systolic (r=0.80, P=0.0002) and diastolic (r=0.66, P=0.0006) blood pressure in controls and in subjects with primary hypertension and were independent of renal function. Serum uric acid concentrations >5.5 mg/dL were found in 89% of subjects with primary hypertension, in 30% with secondary hypertension, in 0% with white-coat hypertension, and in 0% of controls. We conclude that serum uric acid is directly correlated with blood pressure in untreated children and that a serum uric acid value >5.5 mg/dL in an adolescent being evaluated for hypertension strongly suggests primary hypertension as opposed to white-coat or secondary hypertension. These results are consistent with the hypothesis that uric acid might have a role in the early pathogenesis of primary hypertension.

Figure 1

Box-and-whisker plot of serum uric acid levels in children with hypertension and normal BP. The mean and SD for serum uric acid levels for children with primary hypertension, secondary hypertension, white-coat hypertension, and normal BP controls are shown. When compared with controls, uric acid levels were significantly higher in children with essential (P=0.000004) and secondary (P=0.008) hypertension.

Figure 2

A, Serum uric acid is plotted against systolic BP for children with normal BP (controls) and primary hypertension. B, Serum uric acid is plotted against diastolic BP for children with normal BP and primary hypertension. Data do not include individuals with secondary hypertension. Solid and dotted lines in both panels represent the best fit and 95% confidence intervals, respectively, and demonstrate the linear relation between uric acid concentration and BP. Pearson correlation coefficients are r=0.8053 (P=0.000004) for systolic BP and r=0.6606 (P=0.0014) for diastolic BP.

Figure 3

No correlation between uric acid and GFR. Serum uric acid is plotted against GFR for children with normal BP and primary hypertension (same population as in Figure 2). The correlation coefficient is r=0.0407.