Objective: The present study examined whether levels of testosterone, sex hormone binding globulin (SHBG), or insulin levels might underlie an increased risk of postmenopausal breast cancer in women with both high waist-tohip ratio and a family history of breast cancer disease that was noted earlier in the Iowa Women's Health Study. Methods: Participants for the current study were selected from 1922 sister groups (3978 women) in the Iowa Women's Health Study cohort. Two groups were included: (1) those with no family history of breast cancer and at least one sister with a high waist-to-hip ratio; or (2) those with a positive family history of breast cancer and at least one sister with a high waist-to-hip ratio. Testosterone, SHBG and insulin were measured by radioimmunoassay from 245 fasting blood samples. Results: Familial correlations among members of 66 families were estimated at 0.32, 0.28 and 0.25 for serum insulin, free testosterone and SHBG; respectively. Fasting serum insulin was significantly higher in breast cancer family history negative women than in family history positive women, in direct opposition to our a priori hypothesis. No significant differences were observed in serum SHBG or free testosterone across family history categories. Conclusion: This study corroborates a genetic component to fasting serum insulin, free testosterone and SHBG levels. It seems unlikely that insulin, SHBG, or testosterone explain the interaction between waist-to-hip ratio and family history of breast cancer among participants in the Iowa Women's Health Study.
Bibliographical noteFunding Information:
The authors thank Chris Korte and Patricia Boland, formerly of Quest Diagnostics. Without the efforts of, and many miles traveled by these two women, the collection of these data would not have been possible. This work was supported by Public Health Service grant CA 39742 from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services. Additionally, some of the results of this paper were obtained by using the program package SAGE, which is supported by a US Public Health Service Resource Grant (1 P41 RR03655) from the National Center for Research Resources.
- Adipose tissue
- Breast neoplasms