Sex hormone binding globulin and risk factors for breast cancer in a population of normal women who had never used exogenous sex hormones

Abstract Background Metformin has been associated with lower breast cancer (BC) risk and improved outcomes in observational studies. Multiple biologic mechanisms have been proposed, including a recent report of altered sex hormones. We evaluated the effect of metformin on sex hormones in MA.32, a phase III trial of nondiabetic BC subjects who were randomly assigned to metformin or placebo. Methods We studied the subgroup of postmenopausal hormone receptor-negative BC subjects not receiving endocrine treatment who provided fasting blood at baseline and at 6 months after being randomly assigned. Sex hormone-binding globulin, bioavailable testosterone, and estradiol levels were assayed using electrochemiluminescence immunoassay. Change from baseline to 6 months between study arms was compared using Wilcoxon sum rank tests and regression models. Results 312 women were eligible (141 metformin vs 171 placebo); the majority of subjects in each arm had T1/2, N0, HER2-negative BC and had received (neo)adjuvant chemotherapy. Mean age was 58.1 (SD=6.9) vs 57.5 (SD=7.9) years, mean body mass index (BMI) was 27.3 (SD=5.5) vs 28.9 (SD=6.4) kg/m2 for metformin vs placebo, respectively. Median estradiol decreased between baseline and 6 months on metformin vs placebo (−5.7 vs 0 pmol/L; P < .001) in univariable analysis and after controlling for baseline BMI and BMI change (P < .001). There was no change in sex hormone-binding globulin or bioavailable testosterone. Conclusion Metformin lowered estradiol levels, independent of BMI. This observation suggests a new metformin effect that has potential relevance to estrogen sensitive cancers.

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Concentrations of sex-hormone binding globulin and corticosteroid binding globulin in serum in relation to cardiovascular risk factors and to 12-year incidence of cardiovascular disease and overall mortality in postmenopausal women.

Clinical Chemistry ◽

10.1093/clinchem/32.1.146 ◽

1986 ◽

Vol 32 (1) ◽

pp. 146-152 ◽

Cited By ~ 80

Author(s):

L Lapidus ◽

G Lindstedt ◽

P A Lundberg ◽

C Bengtsson ◽

T Gredmark

Keyword(s):

Risk Factors ◽

Cardiovascular Disease ◽

Body Mass Index ◽

Body Mass ◽

Significant Risk ◽

Sex Hormone ◽

Sex Hormone Binding Globulin ◽

Hormone Binding ◽

Corticosteroid Binding Globulin ◽

Overall Mortality

Abstract We determined sex-hormone binding globulin (SHBG) and corticosteroid binding globulin (CBG) by radioimmunoassay of serum samples from a group of 253 women, who were 54 or 60 years old when first studied in 1968-69. The SHBG concentration was highly significantly and inversely related to body mass, body mass index, waist-to-hip circumference ratio, and serum triglyceride concentration; CBG concentration was inversely related to body mass and body mass index. The concentration of neither protein was related to whether or not the subject smoked. Decrease in the concentration of SHBG, but not of CBG, was a significant risk factor for 12-year overall mortality. The plot of the 12-year incidence of myocardial infarction vs SHBG concentration was U-shaped. We recommend that SHBG be included when serum androgens or estrogens are being evaluated as risk factors for cardiovascular disease and death.

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