Objective: To determine whether transdermal oestrogen (E2) preparations alter total cortisol and cortisol binding globulin (CBG) concentration similarly to oral E2 treatment.
Methods: This cross-sectional, observational study compared levels of total serum cortisol, CBG, the free cortisol index (FCI) and salivary cortisol levels (as a measure of free cortisol) in oestrogen naïve women (n=15), women taking oral oestrogen (n=14) and females using transdermal oestrogen treatment (n=8). 37 women attending the endocrine unit at our Hospitals were studied. Single blood and salivary samples were collected from each patient, between day 1018 of their menstrual cycle (where applicable) at 08300930 am. The study was approved by the local Research Ethics Committee.
Results: Total circulating cortisol levels were higher in those receiving oral E2 than either the transdermal group (P<0.01) or controls (P<0.01, oral group 645±139 nmol/l, mean±S.D. vs transdermal 368±111 vs control 399±92). CBG was similarly higher in those on oral E2 (with no difference observed between control and transdermal subjects (oral group 112±39 mg/l vs transdermal 51±12 (P<0.05) vs control 50±21 (P<0.01)). The FCI and salivary concentrations were similar between the groups (Salivary cortisol: oral group 5.5±1.8 nmol/ml vs transdermal 5.5±2.0 vs control 5.2±2.1).
Conclusions: Oral E2 increased total cortisol concentrations, by increasing levels of CBG. Transdermal E2 did not result in increased CBG and thus did not alter the level of total cortisol. Free cortisol was appropriately similar between control subjects and those on both oral and transdermal E2. This pilot study indicates that transdermal E2, unlike oral E2 has no significant effect on cortisol levels. It is probably not necessary to discontinue transdermal E2 in patients undergoing assessment of the HPA axis or hydrocortisone replacement. Transdermal E2 preparations may be the most suitable form of E2 replacement for many hypopituitary women.
01 - 05 Apr 2006
European Society of Endocrinology