Endocrine Abstracts

Introduction: Metformin treatment was associated with decreased risk of various cancers including breast cancer. Exposure to sex steroid is related with increased risk of breast cancer. In this study, we aimed to evaluate the effect of metformin treatment on serum levels of sex steroids and sex hormone binding globulin (SHBG) in postmenopausal women with type 2 diabetes mellitus.

Methods: Postmenopausal patients with newly diagnosed type 2 diabetes were recruited to the study. Before starting life-style modifications and metformin treatment anthropometric measurements were done and fasting blood samples were collected in order to evaluate insulin, glucose, HbA1c, serum levels of sex hormones, and SHBG. All of the basal tests were repeated for each subject at the end of 12 weeks.

Results: At the end of 12 weeks, 36 patients completed the study and were included into analyses. Five of 36 patients did not use metformin due to gastrointestinal side effects or noncompliance with therapy. Remaining patients used at least 500 mg to maximum 2000 mg/day of metformin treatment. Mean body-weight and body fat mass, fasting insulin, HbA1c levels significantly decreased in patients who used metformin. Patients receiving metformin treatment also showed significant decrease in testosterone (−28%), oestradiol (−9%), and oestrone levels (−11.5%), and significant increase in DHEAS (8.9%) and SHBG (4.5%) levels. A borderline significant decrease was seen in androstenedione levels as well. Fasting plasma glucose and oestrone sulphate levels did not change significantly. When compared to the patients who did not use metformin therapy, changes in oestradiol levels were significant, and changes in estrone and testosterone levels marginally significant in patients receiving metformin.

Conclusion: Metformin treatment may have favourable effect on breast cancer risk through decreasing androgen and oestrogen levels in postmenopausal type 2 diabetic patients.