Luteal phase oral dexamethasone administration alters endometrial steroid milieu.

We previously published the DexFEM trial, which showed that in women with heavy menstrual bleeding (HMB), oral dexamethasone reduces menstrual blood loss. Here, we report a pharmacodynamic analysis exploring the likely mechanism for this effect. We studied oral dosing with dexamethasone during the mid-luteal phase of two menstrual cycles (1.5 mg daily, 5 days) in five women with HMB (six recruited aged 41–50 years, one withdrew before treatment). Steroid hormones were profiled in serum and endometrium by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We found that following oral dosing, dexamethasone reached the endometrium and that, compared to the preceding control cycle, cortisol (active), cortisone (inactive) and intermediate 11-deoxycortisol were reduced in all samples assessed, both endometrial (n = 4) and serum (n = 5). Concentrations of androgens, androstenedione and testosterone were reduced in serum but not in all tissue samples. This proof-of-concept pharmacodynamic study supports the inference that dexamethasone is effective in HMB by altering endometrial glucocorticoid concentrations.