Growth Hormone 1 T1663A Polymorphism, Recreational Physical Activity and BMI, and Breast Cancer Risk in Chinese Women.

To evaluate the relationship between the growth hormone 1 (GH1) T1663A polymorphism, recreational physical activity and body mass index (BMI) with reference to breast cancer, we conducted a case-control study with 669 cases of breast cancer and 682 population-based controls in Jiangsu Province, China. A structured questionnaire was used to elicit detailed information. All subjects completed an in-person interview. GH1 genotypes were identified using PCR-RFLP methods. Odds ratios (ORs) were estimated with an unconditional logistic model. The distribution of GH1 genotypes was not significantly different between controls and cases (χ2=2.576, P=0.276). Results of stratified analysis by the participation status of the recreational physical activity showed that the persons with GH1 A allele were at a decreased risk of breast cancer (adjusted-OR=0.66; 95% CI, 0.50-0.87) only among inactive individuals. Stratified analysis by BMI showed that the genotype A/A was associated with a decreased risk of breast cancer only among individuals of the BMI<25 (adjusted-OR=0.80; 95% CI, 0.66-0.98). The findings of this study suggest that recreational physical activity and BMI may modify any association between the GH1 T1663A polymorphism and breast cancer risk.