Further studies on pituitary and ovarian function in women receiving hormonal contraception

Pituitary and ovarian function was evaluated in women receiving 3 combined oral contraceptive preparations. Basal levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH) and gonadotropic responses to gonadotropic releasing hormone (GnRH) were studied in 36 healthy, regularly ovulating women in the early follicular and mid-luteal phases of their menstrual cycle (non-treatment, control). These same women were then divided into 3 groups with 12 volunteers in each. Each group received an oral contraceptive preparation cyclically for 3 months. The preparations were: Nordette (30 microgram ethinyl estradiol and 150 microgram d-norgestrel), Nordiol (50 microgram ethinyl estradiol and 250 microgram d-norgestrel) and Biphasil (50 microgram ethinyl estradiol and 50 microgram d-norgestrel X 11 days and 125 microgram d-norgestrel X 10 days). In the third month of treatment, the tests were repeated on day 21, i.e. after 21 active pills, and on day 28, i.e. after 21 active and 7 inactive tablets. On active therapy, basal FSH and LH were similarly suppressed in the 3 groups. LH had varied responses to a bolus of GnRH, whilst the FSH responses were similar in the 3 groups. After 7 days of inactive tablets, basal FSH and LH had returned to pre-treatment, early follicular phase levels. However, the LH responses to a bolus of GnRH varied in the 3 groups, but again, no differences were noted in the FSH responses. Basal FSH, LH and E2 recovered earlier in the Nordette group during the 7 days of inactive tablets.