Abstract
The effect that synthetic steroid components of different oral contraceptives have on the assay system for measurement of sex hormone binding globulin (SHBG)-binding capacity, has been examined. Interference with the assay was not demonstrable at therapeutic levels of the drugs. d-Norgestrel was the only steroid studied which bound to SHBG with an affinity comparable to the endogenous sex hormones; it also tended to decrease SHBG-binding capacity, whereas preparations containing low levels of norethisterone increased the binding capacity. We suggest that measurement of changes in SHBG-binding capacity in subjects taking oral contraceptives may prove useful in indicating changes in sex hormone balance, particularly in view of the well-recognised side-effect of these drugs.