A new superagonist of GnRH for inhibition of ovulation in women

Characterizing pituitary response to a gonadotropin-releasing hormone (GnRH) antagonist in monkeys: tonic follicle-stimulating hormone/luteinizing hormone secretion versus acute GnRH challenge tests before, during, and after treatment

Pituitary sensitivity to a gonadotropin-releasing hormone (GnRH) challenge test before, during, and after GnRH antagonist administration was compared in four ovariectomized female monkeys receiving GnRH antagonist intramuscularly (IM) at increasing doses of 0.3, 1.0, and 3.0 mg/kg/day over 9 days. Three days before and 3 days after treatment, monkeys received vehicle alone. On experiment days 4, 7, 10, 13, and 16, 100 micrograms of GnRH was administered intravenously (IV) and blood drawn at 0 and 30 minutes. Before treatment, tonic follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were 248 +/- 105 and 178 +/- 31 ng/ml, respectively; after 0.3 mg/kg/day of GnRH antagonist, FSH and LH decreased to 30 +/- 6 and 41 +/- 4 ng/ml, respectively. After treatment with either 1 mg/kg/day or 3 mg/kg/day of GnRH antagonist, both gonadotropins were undetectable in serum. Monkeys with lower initial levels of gonadotropins were suppressed by 48 hours after GnRH antagonist, while those with higher tonic gonadotropins were suppressed 6 days later (FSH: r = 0.992; LH: r = 0.833). The data show that initial physiologic status is predictive of the rapidity of the suppression response induced by a GnRH antagonist and that, after achieving pituitary suppression, responsivity to an IV GnRH challenge test may be restored before normal tonic FSH/LH secretion is regained.

Gonadotropin releasing hormone analogs for female contraception by inhibition of ovulation

One hundred and one healthy regularly ovulating women used two superactive GnRH agonists, Buserelin and Nafarelin, for contraception for 3-26 months. The superagonists were administered once daily by a nasal spray. The treatment was initiated on one of the first 3 days of the menstrual cycle. Seventy-one volunteers used 200, 400 or 600 micrograms of Buserelin for contraception for 3-26 months. Normal ovulation was disturbed in all but 3 of 628 treatment months. No pregnancy occurred. Fifty-three women had regular or sparse menstrual-like bleedings during treatment while 18 developed amenorrhea. Normal ovulation and fertility rapidly returned after cessation of therapy. Thirty women received 125 or 250 micrograms of Nafarelin intranasally once daily for 3 months. The treatment consistently inhibited ovulation without serious side effects. The inhibition of ovulation by prolonged continuous intranasal GnRH agonist therapy is a promising new lead to peptide contraception in women.