The Tromsø Study. Distribution and population determinants of gamma-glutamyltransferase.

Gamma-glutamyltransferase was measured in 10,942 males aged 12-62 years and 10,840 females aged 12-59 years screened in a health survey program. The distribution was right-skewed, with medians of 17 and 12 units/liter for males and females, respectively. Fewer than 5.5% of the males and 1.5% of the females had values exceeding 50 units/liter, reflecting the modest use of alcohol in Norway. In sex-specific multiple regression analyses, gamma-glutamyl-transferase showed a strong positive association with body mass index, alcohol use, and total serum cholesterol and a somewhat weaker positive association with serum triglycerides, high density lipoprotein cholesterol, heart rate, blood pressure, use of analgesics, and time since last meal. Strong negative associations were found for coffee consumption, hour of the day at which the examination was performed and, in males, physical activity. In females, use of oral contraceptives and menopause were positively associated with gamma-glutamyltransferase, whereas pregnant females had lower values. In conclusion, the gamma-glutamyltransferase level in the Tromsø population was low, with marked and consistent sex differences which probably are physiologic. Within its normal range, gamma-glutamyltransferase has many other, even stronger determinants than alcohol consumption.