Distribution of urinary gamma-glutamyltransferase activity in 40- to 74-year-old Japanese women

Urinary gamma-glutamyltransferase (u-γGT) concentration (U/L) and excretion (urinary creatinine-corrected u-γGT; u-γGT/u-Cre, U/g creatinine) are useful markers for kidney disease. However, there is limited information available on u-γGT and u-γGT/u-Cre distribution in the elderly Japanese population. In this study, we investigated the distribution of u-γGT and u-γGT/u-Cre in 113 Japanese women aged 40–74 years. The u-γGT was assessed from spot urine samples (collected from 09:00 to 14:00) spectrophotometrically according to the Japan Society of Clinical Chemistry reference measurement procedure using l-γ-glutamyl-3-carboxy-4-nitroanilide as the substrate. The u-Cre was measured enzymatically using creatininase, creatinase, sarcosine oxidase, and peroxidase. None of the participants was diagnosed with any kidney disease. Median u-γGT and u-γGT/u-Cre values (central 95% interval values) were 29.7 (5.3–144.0) U/L and 57.9 (32.9–122.7) U/g creatinine, respectively. The distribution of u-γGT tended to decline with age. There was a statistically significant difference in the u-γGT value between the 40-59- and 60-74-year-old groups. In contrast, there was no significant difference in the u-γGT/u-Cre between each age group. The u-Cre level also declined with age. It is suggested that the decline of u-γGT with aging would be masked by the u-Cre correction.