Objective: The purpose of this study was to evaluate the effects of the contraceptive patch and an oral contraceptive (OC) on serum concentrations of estrogen-sensitive hepatic proteins, ethinyl estradiol (EE) and levonorgestrel (LNG).
Methods: Twenty-four women were randomized to receive three cycles of a contraceptive patch that delivers EE 20 microg/day and norelgestromin 150 microg/day or an OC that contains EE 35 microg and norgestimate 250 microg. Blood samples were taken at baseline and at the end of Cycle 3. Serum levels of sex-hormone-binding globulin (SHBG), thyroxine-binding globulin (TBG), corticosteroid-binding globulin (CBG) and C-reactive protein (CRP) were quantified by immunoassay methods. EE and LNG levels in patch users were measured by radioimmunoassay (RIA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay. The paired t test and Student's t test were used for statistical analysis.
Results: Nineteen women completed the study (patch, n=10; OC, n=9). Treatment with both the patch and OC resulted in significant increases from baseline in SHBG, TBG and CBG. The increase in CRP was significant in the patch group and approached significance in the OC group. The increases in SHBG and TBG observed with the patch were significantly greater than those associated with the OC. By way of RIA and LC-MS/MS assay methods, the patch was associated with mean EE levels of 114 and 111 pg/mL, respectively.
Conclusions: The serum concentrations of estrogen-sensitive hepatic proteins and EE associated with the patch suggest that this new contraceptive system may have relatively large net estrogen effects.