The influence of norethisterone oenanthate on ovarian function.

Two-hundred mg norethisterone oenanthate was injected im into five women on the fifth or sixth day after the onset of the menstrual bleeding. The plasma levels of oestradiol and progesterone were measured during one control cycle before the injection and then for three months or until ovulation occurred. According to the plasma progesterone pattern the five women ovulated during the control cycle. After the injection ovulation was delayed in all the subjects. In two of the participants the first ovulation occurred around 55 days after the injection, while in two others ovulation was delayed about 80 days. The fifth woman did not ovulate until 16 weeks after the injection. The treatment did not suppress the plasma levels of oestradiol below the levels seen in untreated women during the follicular phase. It is concluded that the treatment with 200 mg of norethisterone oenanthate im can inhibit ovulation for an unpredictable time, but that the ovulatory pattern is restored within 12 weeks in most of the women.