Ablation of folliculogenesis in women by a single dose of gonadotropin-releasing hormone agonist: significance of time in cycle

Quantitative approaches in clinical reproductive endocrinology

Understanding the human hypothalamic-pituitary-gonadal (HPG) axis presents a major challenge for medical science. Dysregulation of the HPG axis is linked to infertility and a thorough understanding of its dynamic behaviour is necessary to both aid diagnosis and to identify the most appropriate hormonal interventions. Here, we review how quantitative models are being used in the context of clinical reproductive endocrinology to: 1. analyse the secretory patterns of reproductive hormones; 2. evaluate the effect of drugs in fertility treatment; 3. aid in the personalization of assisted reproductive technology (ART). In this review, we demonstrate that quantitative models are indispensable tools enabling us to describe the complex dynamic behaviour of the reproductive axis, refine the treatment of fertility disorders, and predict clinical intervention outcomes.

A case of atypical absence seizures induced by leuprolide acetate

We report a case of a 13-year-old female with atypical absence seizures induced by prolonged administration of long-acting leuprolide acetate (LA). This patient had brain involvement resulting from chemotherapy and radiotherapy for a medulloblastoma. At 13 years of age, administration of long-acting LA was started. After the third dose of long-acting LA, atypical absence seizures appeared. After discontinuing long-acting LA, the seizures stopped without administration of any antiepileptic drugs. However, 2 years, 6 months later, the same seizures again appeared. On the basis of the findings of endocrinologic investigations and the reported data of pharmacokinetics of LA, we speculate that her seizures were induced by LA and that the seizures were associated with the presence of brain damage in the patient. Care should therefore be taken when using long-acting LA or other gonadotropin-releasing hormone analogues for pediatric patients with diffuse brain damage.

The luteinizing hormone surge--the final stage in ovulation induction: modern aspects of ovulation triggering

OBJECTIVE

To compile updated information regarding gonadotropin secretion, specifically the physiology of the midcycle LH surge, in natural cycles and under various ovulation induction protocols.

DATA IDENTIFICATION AND SELECTION

Studies that deal with the clinical aspects of LH surge manipulation or substitution were identified through literature and Medline searches.

RESULTS

Three major regulatory factors have been identified as participants in the induction of the midcycle gonadotropin surge. These are hypothalamic GnRH secretion, ovarian and adrenal steroids, and less well-characterized ovarian peptide hormones. Gonadotropin-releasing hormone pulsatility is regulated by a complex mechanism that integrates multiple neurotransmitters and sex steroids. Estradiol plays a central role in the pituitary secretion of LH, which also is influenced by P concentrations. Gonadotropin surge attenuating factor also has been implicated in the regulation of timing and amplitude of the LH surge. Human chorionic gonadotropin is used extensively as a LH surrogate, but its use is associated with a number of disadvantages. Induction of an endogenous LH surge through use of the flare effect of GnRH analogues has been examined more recently and has been found to have several advantages. Recombinant human LH is in the final stages of clinical testing.

CONCLUSION

Although much is known about the physiology of the midcycle LH surge and its variations under different clinical conditions, new approaches to the induction or substitution of the LH surge currently are being examined and learned. The introduction of recombinant gonadotropins into clinical practice is likely to influence ovulation induction and IVF practice to a significant degree in the near future.

Gonadotropin-releasing hormone agonist testing of pituitary-gonadal function

The development of gonadotropin-releasing hormone (GnRH) agonists has provided a unique means to functionally assess the pituitary-gonadal axis in both males and females. These agonists, when given in a dose sufficient to stimulate the gonadotropes and induce a gonadal steroid response, have provided insights into normal reproductive physiology, hyperandrogenic conditions such as the polycystic ovary syndrome (PCOS), and disorders of pubertal development. This review provides an overview of the use of such agonists as probes of the functional status of the pituitary-gonadal axis in both normal and abnormal reproductive states.

The efficacy of a combination administration of gonadotropin-releasing hormone agonist and gonadotropins for controlled ovarian hyperstimulation in IVF program

In 105 patients with the past history of poor response to the previous controlled ovarian hyperstimulation (COH) due to poor follicular growth or premature LH surge, the efficacy of pituitary suppression with gonadotropin-releasing hormone agonist (GnRHa) in IVF/GIFT program was evaluated in 112 cycles of COH using a combination regimen of leuprolide acetate (Lupron) and FSH/hMG or pure FSH from May to December, 1989. After suppression phase, serum E2 and progesterone levels decreased significantly, but there was no change in serum LH and FSH levels. There was no occurrence of premature LH surge during COH. Eleven cycles (9.8%) were cancelled, and 3 cycles (3.0%) failed in the transvaginal oocytes retrieval. The 7.00 +/- 3.32 follicles (FD greater than or equal to 12 mm) were observed, and 6.11 +/- 4.15 oocytes were retrieved. The 3.59 +/- 2.57 oocytes were fertilized and cleaved with the cleavage rate of 55.7%. In 83 IVF patients, 4.08 +/- 2.39 embryos were transferred, and 16 pregnancies were obtained with the pregnancy rate per ET of 19.3%. In 6 GIFT patients, 7.83 +/- 3.31 oocytes were available for transfer. When compared with the previous 108 cycles, the cancellation rate during COH was decreased and all the parameters of the outcome of COH including the pregnancy rate were increased. These data suggest that GnRHa therapy for pituitary suppression is an effective adjunct to the current gonadotropin regimens for COH in IVF/GIFT and can increase the probability of oocytes retrieval and pregnancy, especially in the previous poor responders.

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.

Chemotherapy-induced premature ovarian failure: mechanisms and prevention

Significant advances have been made in the previously unexplored areas of the mechanisms involved in cyclophosphamide (CTX)-induced ovarian toxicity and the protective effects of luteinizing hormone-releasing hormone (LHRH agonists. The structure and function of granulosa cells and oocytes are affected by the chemotherapeutic agent, CTX. Results of experiments in female rats indicate that LHRH agonists may protect the ovaries from the toxic effects of chemotherapy. The protective effect may be related to the inhibition of ovarian mitotic activity during LHRH agonist administration. This inhibition is much more pronounced in female compared to male rats. This may be related to the observed better gonadal protective effects in females compared to males. Further experiments are underway to determine whether similar protective effects occur in female primates.

Pituitary-ovarian responses to nafarelin testing in the polycystic ovary syndrome

To investigate the basis of polycystic ovary syndrome, we examined the responses of patients to nafarelin, a specific gonadotropin-releasing-hormone agonist, given to stimulate pituitary and gonadal secretion. We compared 16 normal women in the follicular phase, 5 normal men, 8 women with polycystic ovary syndrome, and 1 woman with polycystic ovary syndrome caused by a 3 beta-hydroxysteroid dehydrogenase deficiency. After 100 micrograms of nafarelin was given subcutaneously, serum follicle-stimulating hormone and luteinizing hormone increased rapidly to peak levels within four hours. The women with polycystic ovary syndrome had a pattern similar to that of the men, with greater early luteinizing-hormone responses (30 minutes to 1 hour) and lower peak follicle-stimulating-hormone responses than normal women (P less than 0.05). Patients with polycystic ovary syndrome responded to gonadotropin stimulation with normal to increased production of plasma estrogens and increased levels of androstenedione at 16 to 24 hours (P less than 0.05). Elevated production of 17 alpha-hydroxyprogesterone was found in all the women with polycystic ovary syndrome and in the men. These abnormal responses were unchanged by pretreatment with dexamethasone to suppress adrenal function. In the patient with the 3 beta-hydroxysteroid dehydrogenase deficiency, both basal and stimulated plasma levels of delta 5-3 beta-hydroxysteroids before the enzymatic block were elevated, whereas plasma levels of 17 alpha-hydroxyprogesterone and androstenedione--the steroids immediately beyond the block--were low. We conclude that women with polycystic ovary syndrome have masculinized pituitary and ovarian responses to stimulation by nafarelin. Our findings suggest that the regulation of the ovarian 17-hydroxylase and C-17,20-lyase activities is abnormal in such women.

Ovarian stimulation by a combination of a gonadotropin-releasing hormone agonist and gonadotropins for in vitro fertilization

In the first of two studies, 20 patients were selected on the basis of tubal infertility and were randomly assigned to two groups receiving different ovarian stimulation protocols. In group A, 10 patients were given follicle-stimulating hormone (FSH), FSH was continued until the criteria for human chorionic gonadotropin (hCG) administration were satisfied. In group B, 10 patients received Buserelin (0.3 ml twice a day subcutaneously) for 14 days to induce pituitary desensitization. Stimulation with FSH was then started, and Buserelin treatment was continued until hCG administration. In the second study, patients were included if they had had at least two previous attempts at ovarian stimulation that failed to reach the stage of follicular aspiration. Ovarian stimulation was conducted with a combination of Buserelin and human menopausal gonadotropin. Use of the gonadotropin-releasing hormone (GnRH) agonist in in vitro fertilization increased the number of oocytes collected, the fertilization rate, the length of the luteal phase and the pregnancy rate. The GnRH agonist also contributed to a generally better ovarian response in patients whose estradiol production had previously responded poorly to conventional ovarian stimulation protocols.

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

Fourteen women with ovulatory menstrual cycles were treated with a superactive agonistic analog of gonadotropin-releasing hormone (6-D-[2-naphthyl]-alanyl)-GnRH (nafarelin). Eight of the women received a single subcutaneous injection of nafarelin during the luteal phase at a dosage of 2, 5, or 100 micrograms for determination of the dose-response and pharmacokinetic characteristics of the drug. All doses stimulated the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Maximal release was obtained with the 5-micrograms dose (mean +/- standard deviation: delta LH = 297 +/- 75 mIU/ml; delta FSH = 29 +/- 7 mIU/ml), and there was no greater release of gonadotropin with the 100-micrograms dose. To investigate the contraceptive potential of nafarelin as a luteolytic agent, six of the women were treated with 100 micrograms of analog by daily injection for 10 days, beginning either 2 to 3 days or 5 to 7 days after ovulation. Gonadotroph desensitization or down-regulation developed within 24 hours, but serum concentrations of LH and FSH did not fall below normal values during treatment. There were no significant changes in mean estradiol or progesterone concentrations. There also was no change in mean length of the luteal phase (13.7 +/- 2.1 days [control] versus 13.6 +/- 1.4 days). Thus, nafarelin, like other superactive analogs of GnRH, does not appear to be clinically useful as a luteolytic agent in contraceptive development.