Oral contraceptives.

Variations in the side chains attached to the gonadal hormones can produce marked changes in the potency of these compounds and can even change their predominant actions. Modification of testosterone renders it less androgenic and greatly enhances its progestational effect. The antifertility action of oral contraceptives may be exerted through any of several mechanisms: supression of follicular development, suppression of ovum expulsion or changes in endometrium or cervical mucus.