New developments in the use of peptide gonadotropin-releasing hormone antagonists versus agonists

Gonadotropin-releasing hormone (GnRH) stimulates the pituitary secretion of both luteinising hormone (LH) and follicle-stimulating hormone (FSH), and thus controls the hormonal and reproductive functions of the gonads. The blockade of the effects of GnRH may be sought for a variety of reasons; for example, to control premature LH surges and to reduce the cancellation rate with the aim of improving the pregnancy rate per treatment cycle or in the treatment of sex hormone-dependent disorders. Selective blockade of LH/FSH secretion and subsequent chemical castration have previously been achieved by desensitising the pituitary to continuously administered GnRH or by giving long-acting GnRH agonists. GnRH analogues are indicated for clinical situations in which the suppression of endogenous gonadotropins (precocious puberty, contraception and controlled ovarian hyperstimulation) or sexual steroids (endometriosis, prostate hyperplasia, cancer and uterine fibroids) is desired. The immediate suppression of the pituitary that is achieved by GnRH antagonists without an initial stimulatory effect is the main advantage of these compounds over the agonists. GnRH antagonists have been developed for clinical use with acceptable pharmacokinetic, safety and commercial profiles. In assisted reproduction, these compounds seem to be as effective as established therapy, but with shorter treatment times, less use of gonadotropic hormones, improved patient acceptance, and fewer follicles and oocytes. All of the current indications for GnRH agonist desensitisation may prove to be indications for a GnRH antagonist, including endometriosis, leiomyoma and breast cancer in women, benign prostatic hypertrophy and prostatic carcinoma in men, and central precocious puberty in children. However, the best clinical evidence has been in assisted reproduction and prostate cancer.

Comparison of a gonadotropin-releasing hormone (GnRH) antagonist and GnRH agonist flare-up regimen in poor responders undergoing ovarian stimulation

OBJECTIVE

To compare the efficacy of flare-up and GnRH-antagonist treatment in poor-responder patients.

DESIGN

Randomized prospective study.

SETTING

Assisted reproduction center.

PATIENT(S)

Fifty-five poor-responder patients undergoing intracytoplasmic sperm injection (ICSI).

INTERVENTION(S)

Thirty patients received GnRH agonist on the 1st day of menstruation, followed by exogenous gonadotropins from the 2nd day. Twenty-five patients received exogenous gonadotropins starting on the second day of menstruation, followed by GnRH antagonist when the leading follicle reached 14 mm in diameter.

MAIN OUTCOME MEASURE(S)

The total dose of FSH administered during the ovarian stimulation, as well as the number of mature oocytes retrieved, embryo quality, fertilization, implantation, and pregnancy rates were evaluated.

RESULT(S)

The number of ampules and units of FSH administered were significantly less in the flare-up than in the antagonistic group. The numbers of mature oocytes retrieved and of top-quality embryos transferred were significantly greater in the flare-up than in the GnRH-antagonist group. The fertilization rate (84% vs. 63%) was significantly higher in the flare-up than in the GnRH-antagonist group. The implantation and pregnancy rate were similar in the two groups.

CONCLUSION(S)

The flare-up protocol appears to be more effective than the GnRH-antagonist protocol in terms of mature oocytes retrieved, fertilization rate, and top-quality embryos transferred in poor-responder patients.

Emerging drugs for endometriosis

Medical treatment of endometriosis relies on drugs that suppress ovarian steroids and induce an hypoestrogenic state that causes atrophy of ectopic endometrium. Gonadotrophin-releasing hormone (GnRH) analogues, danazol, progestogens and oestrogen-progestin combinations have all proven effective in relieving pain and reducing the extent of endometriotic implants. However, symptoms often recur after discontinuation of therapy and hypoestrogenism-related side effects limit the long-term use of most medications. Furthermore, these therapies are of limited value in patients with a desire to become pregnant because they inhibit ovulation. An important target for current research is to identify effective therapies that can be safely administered in the long term. GnRH analogues with add-back therapy, progestogens and continuous oral contraceptive are options available for a medium or long-term systemic treatment. Mifepristone, an antiprogestogen, may constitute an alternative if encouraging preliminary data on its effectiveness and tolerability are confirmed. A very appealing area of interest is the possibility of treating endometriosis without suppressing ovarian function. Aromatase inhibitors might have such characteristics as they have been shown to inhibit oestrogen production selectively in endometriotic lesions, without affecting ovarian function; the clinical role of these drugs in the treatment of endometriosis is under evaluation. Levonorgestrel medicated intrauterine device has proven effective in relieving dysmenorrhoea associated with endometriosis, as well as pain associated with rectovaginal endometriosis. Although a systemic absorption is present determining side effects, this approach is promising in the long-term management of this condition. A fundamental objective of research in endometriosis treatment is to develop new therapeutic approaches based on the findings from experimental studies on the aetiopathogenesis of the disease; current research is focusing on anti-inflammatory drugs and modulators of the immune system. TNF-binding protein-1 and IL-12 have proved effective in reducing endometriotic lesions in animal models, while pentoxifylline and INF-alpha 2b have shown encouraging results in clinical studies. This area may be of paramount importance in the near future in order to develop a therapy that could prevent or eradicate endometriosis rather than merely relieving the symptoms.

Opinion and evidence for treatments in endocrine disorders

New treatments and treatment protocols for endocrine disorders are evolving rapidly, and research and development activity in the endocrinology field is high. Optimal therapy remains contentious in some areas. To help you keep up-to-date with the latest advances worldwide on all aspects of drug therapy and management of endocrine disorders, this section of the journal brings you information selected from the rapid drug news alerting service Inpharma Weekly. Each issue contains easy-to-read summaries of the most important research and development news, clinical studies, treatment guidelines, pharmacoeconomic and adverse drug reaction news, and expert opinion pieces published in the world's top endocrinology journals.

Modified natural cycle using GnRH antagonist can be an optional treatment in poor responders undergoing IVF

PURPOSE

To investigate the efficacy of gonadotrophin-releasing hormone (GnRH) antagonist supplementation during natural cycles in poor responders undergoing IVF-ET treatment.

METHODS

We retrospectively evaluated 540 cycles of 433 suitable patients who were divided by treatment protocol into modified natural, antagonist, and long agonist groups. There were 52 modified natural cycles with GnRH antagonist supplementation, 200 stimulated cycles with GnRH antagonist, and 288 long GnRH agonist cycles. Cycle characteristics and treatment outcomes were compared between the groups.

RESULTS

The mean number of oocytes retrieved in the modified natural group was significantly lower than in the stimulated antagonist and long agonist groups (1.4 +/- 0.5 vs. 2.3 +/- 1.1 and 2.5 +/- 1.1, respectively, p < 0.05). The respective implantation and pregnancy rates were 10% and 14.3%, 6.75% and 10.2%, and 7.4% and 10.6%. Cycle outcome and cycle properties were similar.

CONCLUSIONS

Modified natural IVF cycle with GnRH antagonist supplementation is a feasible alternative to ovarian stimulation protocols in poor responders.

GnRH-antagonists in reproductive medicine

Suppression of sex steroid production based on desensitisation and down-regulation of pituitary gonadotropin-releasing hormone (GnRH)-receptors by agonistic GnRH-analogues resulting in the blockage of gonadotropin release from the anterior pituitary gland is a well-established approach in a variety of clinical conditions. Antagonistic analogues of GnRH exert their effect by competing with endogenous GnRH for pituitary binding sites. Because of the lack of any intrinsic activity of these compounds, the characteristic initial 'flare-up' effect of GnRH-agonist administration is absent. A more rapid suppression of gonadotropin release from the pituitary gland can be achieved, enabling shorter treatment regimes in ovarian hyperstimulation for assisted reproduction. As yet, GnRH-antagonists have attained market approval only for the indication of premature luteinizing hormone (LH) surge prevention in controlled ovarian hyperstimulation and palliative treatment of advanced prostatic cancer. However, GnRH-antagonists may be useful in a variety of other malignant and non-malignant indications where rapid sex steroid suppression is desired, such as uterine leiomyomas, endometriosis, gynaecological cancers or benign prostatic hyperplasia. In the context of infertility treatment, available data on the application of GnRH-antagonists in the treatment of endometriosis and uterine leiomyomas are reviewed.

Consensus statement. Workshop on therapeutic resistance in breast cancer: impact of growth factor signalling pathways and implications for future treatment

Anti-hormones (notably tamoxifen), chemotherapy and modern radiotherapeutic approaches are invaluable in the management of breast cancer, and collectively have contributed substantially to the improved survival in this disease. Moreover, there is promise that these successes will continue with the emergence of other endocrine agents (for example, aromatase inhibitors and pure anti-oestrogens). However, de novo and acquired resistance comprises a significant problem with all treatment approaches examined to date. This Workshop aimed to evaluate the contribution made by growth factor signalling pathways in the various resistant states, primarily focusing on resistance to anti-hormonal strategies and spanning experimental models and, where possible, clinical breast cancer data. The successes and limitations of therapeutic targeting of these pathways with various signal transduction inhibitors (STIs) were evaluated in model systems and from emerging clinical trials (including epidermal growth factor receptor inhibitors such as gefitinib). It was concluded that growth factor signalling is an important contributor in the development of endocrine resistance in breast cancer and that use of STIs provides a promising therapeutic strategy for this disease. However, the cancer cell is clearly able to harness alternative growth factor signalling pathways for growth and cell survival in the presence of STI monotherapy and, as a consequence, the efficacy of STIs is likely to be limited by the acquisition of resistance. A number of strategies were proposed from studies in model systems that appeared to enhance anti-tumour actions of existing STI monotherapy, notably including combination therapies targeting multiple pathways. With the increased availability of diverse STIs and improved drug delivery, there is much hope that the more complex therapeutic strategies proposed may ultimately be achievable in clinical practice.

Giant invasive pituitary adenoma extending into the sphenoid sinus and nasopharynx: report of a case with intraoperative cytologic diagnosis

BACKGROUND

Invasive pituitary adenomas involving the skull base are difficult to distinguish from other, more aggressive tumors. Intraoperaive diagnoses are crucial for deciding the course of treatment.

CASE

A large mass extending from the sella turcica to the sphenoid sinus and nasopharynx was identified in a 42-year-old male. Because of the lack of endocrine abnormalities and lack of an apparent rise in pituitary hormones, preoperative diagnoses included chordoma, chondrosarcoma, meningioma and pituitary adenoma. Tumor fragments were easily squeezed into a thin layer of cells for cytologic specimens. Uniform, round tumor cells were arranged in minimally cohesive cell sheets and possessed regular, ovoid nuclei with a fine chromatin pattern and granular cytoplasm with prominent Golgi areas. The cytologic features indicated a probable diagnosis of pituitary adenoma and excluded other possibilities. Immunohistochemical demonstration of prolactin and ultrastructural features established the final diagnosis of prolactinoma. With the administration of bromocriptine, a large reduction in tumor size occurred. As compared to frozen sections, cytologic preparations are more effective for the intraoperative diagnosis of pituitary adenomas. Such neoplasms should always be included in the differential diagnosis of tumors involving the skull base.

Rapid re-enlargement of a macroprolactinoma after initial shrinkage in a young woman treated with bromocriptine

We report the case of a macroprolactinoma in a 32-year-old woman, who presented with secondary amenorrhea, galactorrhea, increased plasma prolactin level (3259 ng/ml), headache and bi-temporal visual field defect. Magnetic resonance imaging showed a large pituitary tumor. The patient responded well to bromocriptine (7.5 mg/day) with improvement of clinical symptoms and normalization of plasma prolactin within a few weeks. After 4 months of treatment, tumor size was also reduced markedly. During continued treatment at the same dose of bromocriptine the plasma prolactin level remained normal, but after 8 months of treatment the patient suddenly complained of worsening of her visual fields, and magnetic resonance imaging indicated re-enlargement of the tumor. Bromocriptine was discontinued and transsphenoidal pituitary surgery was performed. After surgery the visual field defect improved, but postoperative plasma prolactin level (1104 ng/ml) and magnetic resonance imaging indicated a residual tumor. Postoperative treatment with quinagolide (0.15 mg/day) resulted in disappearance of all clinical symptoms, normalization of prolactin level and a reduction in size of the residual tumor. This case demonstrates that a dissociation of the inhibitory effect of bromocriptine on tumor size and prolactin level may rarely develop during the course of drug treatment in a patient with macroprolactinoma.

Why is the clinical acceptance of gonadotropin-releasing hormone antagonist cotreatment during ovarian hyperstimulation for in vitro fertilization so slow?

The use of GnRH antagonist rather than agonist cotreatment during ovarian hyperstimulation for IVF is not widely accepted. Possible benefits, current shortcomings, and avenues for future development are discussed.

Repeated transsphenoidal surgery to treat recurrent or residual pituitary adenoma

Object. In this paper the authors describe the indications for and the results and complications of repeated transsphenoidal surgery (RTSS) to treat recurrent or residual pituitary adenoma.

Methods. A retrospective review was conducted of 96 consecutive patients who underwent RTSS to treat recurrent or residual pituitary adenoma. Ninety-six patients underwent RTSS: 42 to treat a recurrent or residual pituitary mass and 54 to treat a recurrent or persistent hormone hypersecretion. There was no case of perioperative death and there was a 1% incidence of major complications. Postoperative endocrinological deficiencies were uncommon unless planned total hypophysectomy was performed to treat Cushing disease. Clinical remission occurred in 93% of patients undergoing RTSS to treat a tumor mass, and 15% of patients initially experienced remission only to face a relapse after a mean of 32 months. Endocrinological remission occurred in 57% of patients undergoing RTSS to treat hormone hypersecretion; most of these patients had Cushing disease. Thirty-five percent of patients with an initial endocrinological remission experienced a relapse of their symptoms after a mean of 31 months (thus, 37% of patients achieved sustained endocrinological remission). We failed to identify factors that accurately predicted initial symptom remission or delayed relapse following RTSS. Ten patients in our series eventually underwent a third transsphenoidal surgery without major complications.

Conclusions. Repeated transsphenoidal surgery is a more effective treatment for recurrent or residual mass than it is for hormone hypersecretion and has acceptable rates of morbidity and mortality. If hypophysectomy is not performed, endocrinological deficiencies are unlikely following RTSS.

Opinion and evidence for treatments in endocrine disorders

New treatments and treatment protocols for endocrine disorders are evolving rapidly, and research and development activity in the endocrinology field is high. Optimal therapy remains contentious in some areas. To help you keep up-to-date with the latest advances worldwide on all aspects of drug therapy and management of endocrine disorders, this section of the journal brings you information selected from the rapid drug news alerting service Inpharma Weekly. Each issue contains easy-to-read summaries of the most important research and development news, clinical studies, treatment guidelines, pharmacoeconomic and adverse drug reaction news, and expert opinion pieces published in the world's top endocrinology journals.

Comparison of GnRH agonists and antagonists in assisted reproduction cycles of patients at high risk of ovarian hyperstimulation syndrome

BACKGROUND

During IVF or ICSI cycles, ovarian hyperstimulation syndrome (OHSS) is a major problem. The aim of this prospective, multicentre, comparative study (using historical controls) was to assess the efficacy of a GnRH antagonist protocol in preventing OHSS in selected patients who had experienced OHSS or had been at risk of OHSS in their previous IVF/ICSI attempt.

METHODS AND RESULTS

Patients underwent a new cycle where the same gonadotrophin protocol was used [same dose of recombinant FSH (rFSH)] but a different protocol was used for pituitary desensitization: cetrorelix 0.25 mg multiple-dose antagonist instead of GnRH agonist long protocol. Cetrorelix 0.25 mg was administered daily, starting when the leading follicle reached a diameter of 14 mm. In other words, rFSH was administered in the new cycle according to the dosage and the step-up or step-down modalities used during the previous cycle, independently of ultrasound findings and serum estradiol (E(2)) levels. Eighty-seven patients entered the study. Out of the 87 cycles involving GnRH agonists, 49 (56.3%) were cancelled and out of the 87 involving GnRH antagonists 28 (32.2%) were cancelled [McNemar's test; 95% confidence interval (CI) -35.8% to -11.2%; P < 0.001]. After GnRH agonist cycles, we recorded 24 cases of OHSS (18 moderate and six severe; 27.6%), whereas after the GnRH antagonist cycles there were 10 cases of OHSS (nine moderate and one severe; 11.5%) (95% CI-26.4% to -5.7%; P = 0.006). There was a statistically significant reduction in the total number of follicles with a diameter >10 mm (Wilcoxon's test; Z = 6.1; P < 0.001) and of E(2) levels on the day of HCG administration (2538 versus 4322.4 pg/ml; P < 0.001) in the GnRH antagonist cycles versus GnRH agonist cycles. Twenty-nine patients had an embryo transfer in the first cycle (76.3% of oocyte retrievals) and 57 in the cycle using GnRH antagonist (96.6%). This 20.3% difference was also significant (Z-test; 95% CI 6.8-36.0%; P = 0.003). After the antagonist cycles, 18 pregnancies (20.7 per initiated cycle; 31.6% per embryo transfer) were obtained.

CONCLUSIONS

Although this study presents some limitations owing to the use of historical controls, our data show a favourable effect of GnRH antagonists in reducing the incidence of OHSS and the number of assisted fertilization cycles cancelled because of the risk of OHSS in high responder patients. As a consequence, GnRH antagonist plus gonadotrophin administration could also increase the percentage of oocyte retrievals and embryo transfers in this high risk group of patients.

A prospective randomized study comparing gonadotropin-releasing hormone agonists or gonadotropin-releasing hormone antagonists in couples with unexplained infertility and/or mild oligozoospermia

OBJECTIVE

To compare the efficacy of GnRH antagonist vs. GnRH agonist administration for controlled ovarian hyperstimulation (COH) in assisted reproduction.

DESIGN

A prospective, randomized trial.

SETTING

Clinical research unit at a tertiary care medical center.

PATIENT(S)

Sixty-five patients with unexplained infertility or mild male subfertility undergoing COH for IUI.

INTERVENTION(S)

Twenty-nine women (group A) were randomized to receive 600 microg of busereline acetate per day starting in the midluteal phase of the cycle (long protocol), whereas 36 women (group B) were treated with 0.25 mg/d of the GnRH antagonist Cetrorelix starting from day 6 of the cycle. The starting dose of recombinant FSH was 150 IU in women of both groups. Insemination was performed 34 hours after hCG injection.

MAIN OUTCOME MEASURE(S)

Clinical and successful ongoing pregnancy rate (PR), measurements of serum FSH, LH, E2, and P, number of recruited follicles, duration of stimulation period, and amount of gonadotropins used.

RESULT(S)

Women in group A required significantly more days of treatment (median: 12.0 vs. 9.0) and significantly more total units of recombinant FSH (median 1,800 vs. 1,550) as compared with the corresponding values of the antagonist group (group B). Serum FSH, LH, E2, and P were significantly higher on the antagonist group on days 2 and 6 of stimulation. However, these differences regress until the day of hCG administration.

CONCLUSION(S)

The GnRH antagonists have facilitated short and simple treatment, and are particularly attractive for administration in women undergoing COH, achieving comparable PR with the long protocol regimen.

GnRH agonist versus GnRH antagonist in oocyte donation cycles: a prospective randomized study

BACKGROUND

The specific role of LH in folliculogenesis and oocyte maturation is unclear. GnRH antagonists, when administered in the late follicular phase, induce a sharp decrease in serum LH which may be detrimental for IVF outcome. This study was performed to evaluate whether the replacement of GnRH agonist (triptorelin) by a GnRH antagonist (ganirelix; NV Organon) in oocyte donation cycles has any impact on pregnancy and implantation rates.

METHODS

A total of 148 donor IVF cycles was randomly assigned to use either a GnRH antagonist daily administered from the 8th day of stimulation (group I) or a GnRH agonist long protocol (group II) for the ovarian stimulation of their donors. The primary endpoints were the pregnancy and the implantation rates.

RESULTS

The clinical pregnancy rate per transfer (39.72%, 29/73 versus 41.33%, 31/75) based on transvaginal scan findings at 7 weeks of gestation, the implantation rate (23.9 versus 25.4%) and the first trimester abortion rate (10.34 versus 12.90%) were similar in the two groups.

CONCLUSION

In oocyte donation cycles the replacement of GnRH agonist by a GnRH antagonist appears to have no impact on the pregnancy and implantation rates when its administration starts on day 8 of stimulation.

Progesterone antagonists and progesterone receptor modulators

Since the discovery of the antiprogestin RU 486 (mifepristone), other compounds have been synthesised that function as pure progesterone antagonists or progesterone receptor modulators. The latter are mixed agonists-antagonists. Mifepristone is usually used to terminate pregnancy but these compounds have numerous other applications in female healthcare. Mifepristone is an excellent agent for emergency contraception. Many progesterone antagonists and progesterone receptor modulators display antiproliferative effects on the endometrium and thus have application in the treatment of endometriosis and uterine myoma without being associated with hypoestrogenism and bone loss. They also have contraceptive potential by suppressing follicular development, blocking the luteinising hormone surge and retarding endometrial maturation. Finally, they have clinical application in GeneSwitch system, a plasmid-based method enabling controlled expression of specific genes (e.g., erythropoietin) using a progesterone antagonist as the inducer.

Ganirelix acetate use in normal- and poor-prognosis patients and the impact of estradiol patterns

OBJECTIVE

To evaluate cycle outcomes in patients with either poor or normal prognosis undergoing IVF treatment with a GnRH antagonist (ganirelix acetate) for LH suppression.

DESIGN

Nonrandomized, noncontrolled, retrospective review.

PATIENT(S)

204 patients, aged 23-41 years, undergoing IVF.

INTERVENTION(S)

Patients completed 225 consecutive cycles of IVF with a GnRH antagonist (Antagon; Organon, Roseland, NJ) for LH surge prevention. Sixty cycles were conducted in patients with a known poor prognosis, whereas 165 were conducted in patients with a normal IVF prognosis.

MAIN OUTCOME MEASURE(S)

Pregnancy rate (PR), for the series as a whole and according to prognosis, and serum E2 patterns.

RESULT(S)

The PR per initiated cycle for the series as a whole was 33.3%. The pregnancy rate was 42.1% per ET for the entire series, with a cycle cancellation rate of 21%. When evaluated by prognosis, the poor-prognosis patients had PRs of 8.3% per attempt and 15% per transfer, whereas the normal-prognosis patients had PRs of 40% per attempt and 45% per transfer. Pregnancy rate did not vary by E2 pattern (drop, plateau, or rise). Oral contraceptive pretreatment was noted to be associated with high cancellation rates in the group of known poor responders, whereas for the group as a whole, cycle outcome was unaffected by the use of oral contraceptives.

CONCLUSION(S)

Use of GnRH antagonists in patients with an a priori poor IVF prognosis results in predictably poor outcomes. Patients without factors predicting poor outcome have acceptable PRs. The pattern of E2 rise immediately after initiation of GnRH antagonists does not predict cycle outcome. Oral contraceptives can be successfully used to schedule antagonist-based IVF cycles but might increase the risk of cycle cancellation in some patient populations.

GnRH antagonist versus long GnRH agonist protocol in poor responders undergoing IVF: a randomized controlled trial

BACKGROUND

This is the first published report of a prospective, randomized, controlled trial comparing a fixed, multi-dose GnRH antagonist protocol with a long GnRH agonist protocol in poor responders undergoing IVF.

METHODS

Sixty-six poor responders were randomized into two groups: the study group received 0.25 mg of cetrorelix daily starting on day 6 of stimulation; the control group received 600 microg of buserelin acetate daily starting in the mid-luteal phase of the preceding cycle. Both groups were given a fixed dose of recombinant FSH (300 IU daily) for stimulation.

RESULTS

There were no significant differences in the cycle cancellation rates, duration of stimulation, consumption of gonadotrophins, and mean numbers of mature follicles, oocytes and embryos obtained. The implantation rates were similar, but the number of embryos transferred was significantly higher for the antagonist group (2.32 +/- 0.58 versus 1.50 +/- 0.83; P = 0.01). The pregnancy rates were also higher in the antagonist group, but the difference was not statistically significant.

CONCLUSION

A fixed multi-dose GnRH antagonist protocol is feasible for patients who are poor responders on a long agonist protocol; however, our study failed to demonstrate an overall improvement in ovarian responsiveness. Clinical outcomes may be improved by developing more flexible antagonist regimens, an approach that requires further evaluation.

Antagonists of activin signaling: mechanisms and potential biological applications

Activins are members of the transforming growth factor-beta (TGF-beta) superfamily that control many physiological processes such as cell proliferation and differentiation, immune responses, wound repair and various endocrine activities. Activins elicit these diverse biological responses by signaling via type I and type II receptor serine kinases. Recent studies have revealed details of the roles of inhibin, betaglycan, follistatin and its related protein follistatin-related gene (FLRG), Cripto and BAMBI in antagonizing activin action, and exogenous antagonists against the activin type I (SB-431542 and SB-505124) and type II (activin-M108A) receptors have been developed. Understanding how activin signaling is controlled extracellularly is the first step in providing treatment for wound healing and for disorders such as cachexia and cancer, which result from a deregulated activin pathway.

Luteal phase defect: myth or reality

Although the diagnosis of luteal phase defect (LPD) has been described convincingly in the research setting, it remains a controversial clinical entity. Apart from many uncertainties that surround the diagnosis of LPD, there is no convincing evidence that LPD is associated with infertility and recurrent abortion. Once diagnosed, the treatment options are empiric and include those that are recommended for unexplained infertility. The efforts to diagnose LPD in patients who have infertility or recurrent abortion are not justified.

[Present and potential uses of mifepristone in gynecology, obstetrics and other medical specialties]

Mifepristone, a derivative of norethindrone, a first generation synthetic progestative, has a very potent antiprogestative activity and to a lesser degree antiandrogenic and antiglucocorticoid activities. This action makes it potentially useful in the treatment of multiple hormone dependent diseases in obstetrics-gynecology as well as in a variety of medical specialties such as neurology, ophthalmology, and oncology. Nevertheless, the label of abortive pill has incited numerous ethical and political debates concerning the permission to market this drug, and this has contributed to the delay in the assessment of the potential indications of mifepristone. Largely under-utilized in practice despite its increasing theoretical benefit, clinical studies should now de conducted. Thus, based on an international review of literature during the last ten years, we have shed light on the present and potential indications of mifepristone in medical practice.

Nuclear hormone receptor co-repressors

Gene silencing is an essential transcriptional regulatory process. Co-repressors mediate gene repression through their recruitment by DNA bound transcriptional silencer proteins. Co-repressors repress gene expression through several mechanisms, mostly investigated on the level of chromatin. Lack or aberrant gene silencing is associated with many defects both on cellular and organismic level. Several human diseases are based on dysregulated co-repressor binding to transcriptional silencers indicating that co-repressor recruitment and the strength of gene silencing must be under strict control. In line with that gene silencing is important for animal development, cellular proliferation and transformation. Co-repressors play also a major role in the treatment of hormone-dependent growing cancers, such as for breast and prostate cancer therapy. The molecular basis of anti-hormone therapy lies in the recruitment of co-repressors to the estrogen or androgen receptors, respectively, which leads to their inactivation and to inhibition of cancer growth. The molecular mechanisms of selected topics are summarized here.

Growth factor signalling networks in breast cancer and resistance to endocrine agents: new therapeutic strategies

Recent evidence demonstrates that growth factor networks are highly interactive with the estrogen receptor (ER) in the control of breast cancer growth and development. As such, tumor responses to anti-hormones are likely to be a composite of the ER and growth factor inhibitory activity of these agents, with alterations/aberrations in growth factor signalling providing a mechanism for the development of anti-hormone resistance. In this light, the current article focuses on illustrating the relationship between growth factor signalling and anti-hormone failure in our in-house tumor models of breast cancer and describes how we are now beginning to successfully target their actions to improve the effects of anti-hormonal drugs and to block aggressive disease progression.