Karlijn Koops1, Peter H.L.T. Bisschop2, Annemieke C. Heijboer3, Jacquelien J. Hillebrand4
(1) Endocrine laboratory and Endocrinology, Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Laboratory Medicine, Endocrine Laboratory, Boelelaan 1117, Amsterdam, The Netherlands, Amsterdam, The Netherlands.
(2) Endocrinology, Amsterdam UMC, University of Amsterdam, Department of Endocrinology and Metabolism, Meibergdreef 9, Amsterdam, The Netherlands, Amsterdam, The Netherlands.
(3) Endocrine Laboratory, Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Laboratory Medicine, Endocrine Laboratory, Boelelaan 1117, Amsterdam, The Netherlands, Amsterdam, The Netherlands.
(4) Endocrine laboratory, Amsterdam UMC, University of Amsterdam, Department of Laboratory Medicine, Endocrine Laboratory, Meibergdreef 9, Amsterdam, The Netherlands, Amsterdam, The Netherlands.
Introduction
Estrogens in combined oral contraceptives (OC) elevate corticosteroid-binding globulin (CBG) concentrations, which interferes with endocrine tests for the pituitary-adrenal axis. Therefore, OC needs to be stopped before these tests, but the minimum time required for CBG to normalize is not known. This study aims to determine the time required for serum CBG and cortisol concentrations to reach plateau after discontinuing oral contraceptives.
Methods
This is a prospective, observational study in 24 healthy women planning to stop OC. Blood samples were taken every week in the morning for 8 weeks: two visits before, and six after stopping OC. CBG was measured using a radioimmunoassay. ‘Time-to-plateau’ was defined as the first week after which weekly change was ≤4.7% (the analytical variation coefficient).
Results
We report on the dynamics of CBG in the first 12 participants (preliminary results), aged 30 ±4.6 years with a body mass index of 25.6 ±3.3 kg/m2. CBG was 137.7 ±18.7 mg/L at baseline and 56.3 ±8.3 mg/L six weeks after stopping OC. 76% of the total decrease was observed in the first two weeks after stopping OC. The median (IQR) time-to-plateau was 4 (4-5) weeks, with all participants having reached plateau after 5 weeks.
Conclusion
Our preliminary data show that, following oral contraceptive cessation, CBG concentrations decline quickly and the decline has stabilized after approximately week 4. Analysis of the entire cohort and serum cortisol concentrations will follow, facilitating substantiated conclusions about the minimal duration of OC-cessation for total cortisol measurements.