Background: Body mass index is directly related to testosterone (total T and free T) and inversely to sex hormone binding globulin (SHBG) cross-sectionally, but little is known about how changes in body fat and androgen markers affect each other over time.

Methods: Participants included 969 white and black women from the Coronary Artery Risk Development in Young Adults (CARDIA) cohort, who were ages 18–30 at entry into the study and were pre- or peri-menopausal 16 years later at the time of the CARDIA Women's Study (CWS). Total T and SHBG, were assayed from specimens drawn at the CWS examination and stored serum from the Years 2 and 10 CARDIA exams. Free T was calculated based on total T and SHBG. Body mass index (BMI) and waist circumference were measured at Years 2, 10 and 16.

Results: Despite clinically significant increases in BMI and waist circumference, total T and free T tended to decline while SHBG remained relatively constant. BMI and waist circumference were directly correlated with free T and inversely correlated with SHBG in cross-sectional analyses. In longitudinal, multivariable analyses, an annualized increase in BMI was inversely related to a concurrent annualized decrease in SHBG (beta = -0.79 ng/dl, s.e. = 0.22 in blacks; beta = -1.07 ng/dl, s.e. = 0.31 in whites). However, early increases in BMI were not related to later decreases in SHBG.

Conclusion: Increases in adiposity are closely tied to decreases in SHBG, but changes in body mass index and SHBG may occur concurrently rather than sequentially.