Association between Serum Gamma-Glutamyl Transferase and Thyroid Cancer in an Ultrasonographically Screened Population

Background and Objectives We reported recently a positive correlation between obesity and thyroid cancer in women. Serum gamma-glutamyl transferase (GGT) is regarded as a marker of exposure to environmental pollutants, cancer-causing xenobiotic. This study was conducted to evaluate the mechanism behind the association of obesity with thyroid cancer. We hypothesized serum GGT may be a surrogate for persistent organic pollutants to explain the connection between obesity and thyroid cancer. Materials and Methods We obtained data from 15,131 subjects who underwent a routine health checkup including thyroid ultrasonography from 2007 to 2008 at the Health Screening and Promotion Center of Asan Medical Center. Suspicious nodules were examined by ultrasonography-guided aspiration. Those with a history of hepatobiliary disease and abnormal result of liver function test were excluded. Serum GGT cut-off points were the 25th, 50th, and 75th sex-specific percentiles. Results A total of 15,131 subjects (7662 men and 7469 women) were screened by thyroid ultrasonography. Thyroid cancers were diagnosed in 260 patients. After adjustment of age, smoking status, alcohol intake, body mass index, compared with the lowest serum GGT quartile, odds ratios (95% confidence intervals) of risk of thyroid cancer were 0.54 (0.28-0.99) for 2nd quartile, 0.92 (0.56-1.50) for 3rd quartile, and 0.61 (0.34-1.09) for 4th quartile in men. In women, the adjusted odds ratios were 1.06 (0.66-1.72), 1.18 (0.77-1.85), and 0.63 (0.38-1.06) for the 2nd, 3rd, and 4th quartile, respectively. Conclusion Elevated GGT is not associated with a higher prevalence of thyroid cancer in either gender when evaluated in a routine health checkup setting.