Intermittent elevation of serum urate and 24-hour urinary uric acid excretion

Abstract

Objectives. Serum urate concentrations fluctuate throughout the day, and may be subject to variation with time. However, monthly variation of urinary uric acid excretion has not been investigated. This prompted us to investigate serum urate and 24-h urinary uric acid excretion in healthy men. Methods. Serum urate and creatinine and 24-h urinary uric acid and creatinine were measured at monthly intervals throughout a 12-month period in 12 healthy men (aged 23-61 yr) from July 2002 to June 2003. Results. The mean age of the 12 healthy men was 35.3 ± 10.5 yr (median 33, range 23-61), and they had mean serum urate concentration 7.1 ± 1.1 mg/dl (range 4.6-10.4), mean serum creatinine 1.0 ± 0.1 mg/dl (range 0.8-1.3) and mean 24-h urinary uric acid excretion 651 ± 189 mg/day/1.73m2 (median 623, range 389-1565). Approximately 20.1 and 20.7% of the measurements displayed above normal serum urate level and daily urinary uric acid excretion of more than 800 mg, respectively. Conclusions. The data presented here demonstrate individual variations in serum urate levels and 24-h urinary uric acid excretions in healthy men with serial measurement. Transient hyperuricaemia and hyperuricosuria are more common than expected, and both transitory and monthly variations are important factors to consider when evaluating the influence of other factors upon serum urate levels and urinary uric acid excretion. Further studies are needed to confirm these results using larger populations. © British Society for Rheumatology 2004; all rights reserved.