Determinants of Steroid Hormones in Black and White Men

Principal Investigator: Susan M. Gapstur, PhD, MPH

A diverse and expanding body of evidence suggests that long-term exposure to elevated levels of endogenous androgenic hormones increases the risk of prostate cancer. Moreover, African-American ancestry, a high-fat diet, obesity, physical inactivity and polymorphisms in the gene encoding the androgen receptor also have been linked to prostate cancer risk. The effect of these lifestyle and genetic factors on prostate cancer etiology could be mediated, at least partly, through alterations in steroid hormone levels or metabolism. However, reasons for the substantial inter-individual variation in hormone levels observed among men have not been adequately studied. The overall objective of the CARDIA Male Hormone Study is to evaluate, in longitudinal analyses, lifestyle and genetic determinants of serum steroid hormone and binding protein levels in approximately 1400 black and white male participants of the Coronary Artery Risk Development in (Young) Adults (CARDIA) Study. This project will provide the first analysis of long-term changes in steroid hormones and the factors that may influence these changes in a biracial population. In addition, this research 1) focuses on the age interval from 20-40, when sex hormone levels are highest and abnormal prostate growth is probably initiated; 2) is cost-effective in that it utilizes previously-collected serum samples and lifestyle data of unusually high detail and quality; and 3) incorporates repeated measures of both hormone levels and their potential determinants over an eight-year period, so that inferences will be enhanced by estimating the relationships between changes in potential determinants over time and changes in hormone levels.