Changes in serum urate and urate excretion with age.

Area of Science:

• Nephrology
• Metabolic Disorders
• Pediatrics

Background:

• Serum urate and fractional excretion of urate (FEUr) are critical indicators of kidney function and metabolic health.
• Understanding normal FEUr development is essential for diagnosing kidney and metabolic disorders.
• Uromodulin-associated kidney disease (UAKD) is a genetic disorder affecting kidney function, potentially impacting urate handling.

Purpose of the Study:

• To characterize the developmental changes in serum urate levels and FEUr from infancy to adulthood.
• To compare FEUr in individuals with UAKD to those with normal kidney function.
• To identify factors influencing serum urate levels across different age groups.

Main Methods:

• Cross-sectional study of 1274 individuals undergoing screening for inherited metabolic disorders.
• Measurement of serum urate, serum creatinine, urinary urate, and urinary creatinine.
• Calculation of fractional excretion of urate (FEUr) and estimated glomerular filtration rate (eGFR).
• Comparison of FEUr and serum urate levels between different age groups and with UAKD patients.

Main Results:

• FEUr was highest in infancy (males 27±21%, females 29±25%), declining rapidly in early life.
• Childhood FEUr averaged ~8%, remaining stable in females but decreasing in males during adolescence and adulthood (males ~5.3%).
• Serum urate in childhood was influenced by age and kidney function; in adulthood, by age, gender, and eGFR.
• UAKD patients exhibited lower FEUr than controls, but with significant overlap.

Conclusions:

• Serum urate and FEUr exhibit distinct developmental trajectories influenced by age, gender, and kidney function.
• FEUr is significantly altered in UAKD, though overlap with normal kidney function complicates diagnosis based solely on FEUr.
• These findings provide normative data for FEUr and highlight its complex regulation throughout life.