Cortisol metabolism after oral contraceptives: total plasma cortisol and the free cortisol index.

Plasma concentrations of cortisol, cortisol resin uptake ratio (cortisol RUR) and free cortisol index (FCI) were measured in women taking combined oestrogen/progestogen and progestogen only oral contraceptives. Compared to control subjects, women taking the combined pill had elevated cortisol and cortisol RUR values in both the morning and afternoon but there was no significant change in FCI. Women taking the progestogen only pill had essentially normal levels of cortisol, cortisol RUR and FCI at both times of the day. As far as could be judged, diurnal variation of total cortisol and FCI remained unimpaired in women taking both types of pill. The FCI measurements indicated that there was no significant increase in metabolically active cortisol in women taking either the combined oestrogen/progestogen or the progestogen only type of oral contraceptive.