Direct non-genomic effects of follicular steroids on maturing human oocytes: oestrogen versus androgen antagonism.

Previously published data have suggested that oestradiol exerts direct beneficial effects on human oocytes during in-vitro maturation and that these effects are at least partly due to a non-genomic action of the steroid at the oocyte surface. Here we provide evidence showing that a non-genomic effect of oestradiol is counteracted by androstenedione. In contrast to these results from in-vitro experiments, in which changes in steroid concentrations are abrupt and the non-genomic responses are rapid, the progressively changing follicular steroid concentrations which occur during in-vivo development may rather have permissive or restrictive effects on the events of spontaneous oocyte cytoplasmic maturation. The oocyte is particularly sensitive at the germinal vesicle stage of development to non-genomic steroid actions. Ovarian stimulation protocols should thus be adjusted so as to avoid androgen predominance at the mid-follicular phase. In patients in whom this condition cannot be met, in-vitro maturation of oocytes may be a solution.