Biologically active cortisol in plasma of oestrogen-treated and normal subjects.

Biologically active (non-protein-bound) cortisol levels in the plasma of 13 women taking oral contraceptives and of 67 normal subjects were compared, using a new method-steady-state gel filtration. Both total and unbound cortisol levels in the 67 normal subjects showed a skew distribution, which was roughly log-normal.Unbound cortisol levels in 11 of the oestrogen-treated women were in the normal range, but the median value was significantly increased in this group. Total plasma cortisol levels in the oestrogen-treated group were, as expected, increased threefold, and all were outside the normal range.