Effects of Oral Contraceptives on Endogenous Hormones, Body Constitution, and Breast Epithelium in Healthy, Young Women

Abstract: This thesis concerns the effects of low-dose oral contraceptives (OCs) on endogenous hormones, insulin-like growth-factor-1 (IGF-1), sexual hormone binding globulin (SHBG), and body constitution in two groups of healthy women aged 19­25 who had never been pregnant. Prolactin concentrations were elevated in a subgroup of present and former users. IGF-1 concentrations were significantly decreased during menstrual cycle days 18­23 in present OC users compared with never users, while no effect was seen during cycle days 5­10. Former users had significantly higher follicle-stimulating hormone (FSH) concentrations than never users. This rebound-like phenomenon peaked one year after cessation of use. High FSH concentrations could increase the number of ovulations and thereby the ovarian cancer risk, especially among intermittent users who may experience repeated rebound peaks. Among present and former users SHBG concentrations were significantly correlated with reported weight gain in connection with OC start. SHBG was not related to the same hormonal and constitutional parameters in former users as in never users. Breast size was significantly larger in present users than in former and never users, and approximately half of the ever users reported breast tenderness or enlargement in connection with OC start. Breast epithelial proliferation rate was studied by means of a new monoclonal antibody, Ki-S5, in 58 women who had undergone reduction mammoplasties and who were born 1940 or later. There was no significant difference in breast tissue proliferation between present, former and never users. Women who had used OCs before the first full-term pregnancy had a significantly higher proliferation rate in the breast tissue than other women, regardless of present OC status. Women who used exogenous hormones and who had a first and/or second degree relative relative with breast cancer had a significantly higher proliferation rate in the breast tissue than other women. A high proliferation rate may increase the risk of developing breast cancer.