Endocrine Abstracts

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 10–18 of their menstrual cycle (where applicable) at 0830–0930 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.