Incresed gamma-glutamyltransferase (GGT) concentration has mainly been used as a biologic marker of alcohol drinking and liver diseases. However, some recent reports have suggested that serum GGT concentration may be an early biomarker of oxidative stress and associated with chronic diseases like hypertension, DM, hyperlipidemia, CHD, stroke etc. In this study, we analysed the factors associated with increased serum GGT level and evaluated the clinical application of serum GGT in predicting the risk of chronic diseases.

The data were collected from 15,546 periodic health examinations, 9,660 males and 5,886 females, done at one university hospital from 2001 to 2003. We analysed self-questionnaire, physical examination and laboratory data. Statistical analyses(t-test, ANOVA, Pearson's correlation analysis, multiple regression analysis and logistic regression analysis) were done by SPSS for windows 10.0.

Mean serum GGT levels were quite different according to age, sex, BMI, smoking and alcohol drinking (all P-value < 0.001), but were not different by regular vitamin intake or not (P-value=0.117). There was significant correlation between serum GGT level and the variables (of age, BMI, blood pressure, Hb, fasting blood sugar, total cholesterol, AST and ALT) (all P-value < 0.001). In sex-specific multiple regression analysis, increased serum GGT level was significantly associated with age, alcohol drinking, smoking, blood pressure, fasting blood sugar and ALT in males (all P-value < 0.001), and with age, alcohol drinking, smoking, Hb, blood pressure, total cholesterol and ALT in females (all P-value < 0.05). In sex-specific logistic regression analysis, increased serum GGT level was significantly associated with risk of ‘clinical abnormalities’. This risk increased about 13-fold in males and 4.6-fold in females for serum GGT level over the third quatile, compared with under the first quartile.

Serum GGT level is increased not only by alcohol drinking or liver diseases, but also by many other factors associated with chronic diseases and behavioral factors. Thus many factors should be considered in evaluating an increase in GGT level, even when within the upper normal range. Serum GGT level may be a predictor for the early development of chronic diseases.