Effect on corpus luteum function of luteal phase administration of a potent gonadotropin-releasing hormone analog (nafarelin)

Comparison of LH concentrations in the early and mid-luteal phase in IVF cycles after treatment with HMG alone or in association with the GnRH antagonist Cetrorelix

Luteinizing hormone (LH) is mandatory for the maintenance of the corpus luteum. Ovarian stimulation for IVF has been associated with a defective luteal phase. The luteal phases of two groups of patients with normal menstrual cycles and no endocrinological cause of infertility were retrospectively analysed in IVF cycles. Thirty-one infertile patients stimulated with human menopausal gonadotrophins (HMG) for IVF to whom the gonadotrophin-releasing hormone (GnRH) antagonist Cetrorelix 0.25 mg was also administered to prevent the LH surge (group I) were compared with 31 infertile patients stimulated with HMG alone (group II). Despite differences in the stimulation outcome, luteal LH serum concentrations were similar in the two groups. LH values dropped from 2.3 +/- 1 IU/l on the day of human chorionic gonadotrophin (HCG) administration to 1.1 +/- 0.7 IU/l on day HCG +2 in group I (P < 0.0001) and from 5.1 +/- 3 to 1.2 +/- 1.7 IU/l (P < 0.0001) in group II. In the mid-luteal phase, LH concentrations were low in both groups. Our results suggest that suppressed LH concentrations in the early and mid-luteal phase may not be attributed solely to the GnRH-antagonist administration. Pituitary LH secretion may be inhibited by supraphysiological steroid serum concentrations via long-loop feedback and/or by the central action of the exogenously administered HCG via a short-loop mechanism.

The use of long-acting gonadotropin-releasing hormone agonist (GnRH-a; decapeptyl) and gonadotropins versus short-acting GnRH-a (buserelin) and gonadotropins before and during ovarian stimulation for in vitro fertilization (IVF)

The efficiency of two ovarian stimulation protocols using different gonadotropin-releasing hormone agonists (GnRH-a) for in vitro fertilization (IVF) was examined and compared with human menopausal gonadotropin (hMG)-only stimulation. Fifty-four patients who had 57 aspiration cycles were treated with protocol 1, which consisted of long-acting GnRH-a D-Trp6 (Decapeptyl Depot) and hMG. Protocol 2 entailed intranasal administration of short-acting GnRH-a (Buserelin) and human menopausal gonadotropin (hMG) in 66 women who underwent 70 aspiration cycles. Fifty-five patients who had 59 ovum pickups (OPU) treated with hMG only served as a control. No differences were observed in cycle parameters and hormonal concentrations among the three groups. The total clinical pregnancy rates per OPU for patients receiving protocols 1 and 2 were 12.3 and 27.1%, respectively (P less than 0.05). The pregnancy loss was significantly lower in protocol 2 than in protocol 1 (26.3 versus 71.4%; P less than 0.05). Our data show superiority of short-acting GnRH-a over the long-acting agents in achievement of pregnancy and its outcome, though neither was significantly different from the hMG-only protocol.

Nafarelin acetate: a gonadotropin-releasing hormone agonist for the treatment of endometriosis

Nafarelin acetate is a gonadotropin-releasing hormone (GnRH) agonist proven as effective as danazol in treating endometriosis. Its proposed mechanism of action is the desensitization of pituitary GnRH receptors leading to a decrease in gonadotropin release, and ovarian hormone serum concentrations similar to those achieved in postmenopausal women. Nafarelin decreases or ablates the physical symptoms associated with endometriosis, and pregnancy rates following therapy with this drug are comparable to rates observed after danazol therapy. Nafarelin is administered by nasal inhalation and has been generally well tolerated. It is associated with a high incidence of adverse effects but they are rarely severe enough to cause withdrawal from treatment, and those occurring most frequently--hot flashes, vaginal dryness, and decreased libido--are a consequence of the hypoestrogenemia induced by the drug. Increased bone turnover occurs in women on nafarelin but biochemical parameters return to pretreatment concentrations by six months after termination of treatment. This agent's place in the therapy of endometriosis will be determined as clinical experience accumulates.

Short-term luteinizing hormone-releasing hormone agonist treatment: prospective trial of a novel ovarian stimulation regimen for in vitro fertilization

Over a period of 4 months, 262 infertile couples participated in a prospective pseudorandom trial of a novel short-term luteinizing hormone-releasing hormone/human menopausal gonadotropin (LH-RH/hMG) treatment; the short-Buserelin-gonadotropin (Hoechst, Hounslow, United Kingdom) regimen. Patients treated with the short-Buserelin-gonadotropin regimen had a significantly higher likelihood of achieving pregnancy than patients treated with the standard clomiphene citrate (CC)/hMG regimen (respectively, 35.5% and 18% per treatment cycle). A significantly higher number of eggs were collected after short-Buserelin-gonadotropin treatment than CC/hMG, but the proportion of patients having a given number of embryos replaced was similar in the two groups. The short-Buserelin-gonadotropin-treated patients were distinguished from the CC/hMG-treated group by significantly lower levels of LH in the late follicular phase and a lower plasma level of estradiol. A detrimental relationship between elevated endogenous LH secretion and failure of implantation has been established. The nature of the short-Buserelin-gonadotropin regimen provokes high levels of endogenous gonadotropin secretion in the early follicular phase and induces a suppression of gonadotropin secretion in the late follicular phase. This may be the physiologic basis of the greater implantation rate after short-Buserelin-gonadotropin treatment than is seen with conventional CC/hMG treatment.

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.