The effect of injectable norethisterone oenanthate on ovarian hormones in Thai women

The ovarian hormones, progesterone and estradiol, as well as norethisterone concentrations were studied in 15 subjects receiving a single intramuscular injection of norethisterone oenanthate. Three treatment groups were studied. The 5 subjects of group A had no additional treatment, the 5 subjects of group B received ethynylestradiol and the 5 subjects of group C received combined ethynylestradiol and norgestrel orally. Additional treatment was for 5 consecutive days 6 weeks after the injection. Blood samples were obtained weekly for 12 weeks post-treatment. All subjects showed a similar pattern of norethisterone concentrations with a range of 3.5–19.5 ng/ml 1 week after injection, declining to levels of less than 0.02 ng/ml at the end of treatment period. Progesterone concentrations of greater than 4 ng/ml indicated that ovulation had occurred in 2 subjects of group A, 5 subjects of group B and 2 subjects of group C during the study period. Serum estradiol concentrations reached pre-ovulatory levels ( $ ̆ 200 pg/ml ) in 4,3 and 2 subjects of group A,B and C, respectively, during the treatment period. With the other subjects, serum estradiol showed lesser increases. Among the 15 Thai women in the study, the median time of ovulation was 11 weeks, with the earliest occurring at 6 weeks. Three women receiving NET-OEN and no other treatment had ovulated by 6 weeks. Thai women in this study appear to be more resistant to the antiovulatory effect of NET-OEN as compared to women in other published studies.