Identification of gonadotropin surge-inhibiting factor (GnSIF) in follicular fluid and its differentiation from inhibin

Gonadotropin surge-inhibiting/attenuating factors: a review of current evidence, potential applications, and future directions for research

Animal studies in the 1980s suggested the existence of an ovarian hormone, termed gonadotropin surge-inhibiting/attenuating factor (GnSIF/AF), that modulates pituitary secretion of luteinizing hormone (LH). Given the importance of identifying regulatory factors of the hypothalamic-pituitary-ovarian axis and the accumulating data suggesting its existence, we conducted a comprehensive literature search using PubMed, Web of Science, Scopus, and Embase to identify articles related to GnSIF/AF. The search generated 161 publications, of which 97 were included in this study. Several attempts have been made to identify and characterize this hormone and several candidates have been identified, but the protein sequences of these putative GnSIF/AF factors differ widely from one study to another. In addition, while the RF-amide RFRP-3 is known foremost as a neuropeptide, some research supports an ovarian origin for this non-steroidal hormone, thereby suggesting a role for RFRP-3 either as a co-modulator of GnSIF/AF or as a gonadotropin-inhibiting factor in the hypothalamus (GnIH). Discovery of the KNDy neurons that modulate GnRH secretion, on the other hand, further encourages the search for substance(s) that modulate their activity and that indirectly affect LH secretion and the hypothalamic-pituitary-ovarian axis. While it has remained an elusive hormone, GnSIF/AF holds many potential applications for contraception, in vitro fertilization, and/or cancer as well as for understanding polycystic ovary syndrome, metabolic diseases, and/or pubertal development. In this review, we rigorously examine the available evidence regarding the existence of GnSIF/AF, previous attempts at its identification, limitations to its discovery, future directions of research, and potential clinical applications.

The early days of IVF outside the UK

In this article the history of IVF in geographical regions outside the UK are traced by pioneers of that time. Following the birth of Louise Brown in 1978, live births after IVF occurred in Australia in 1980, in the USA in 1981 and in Sweden and France in 1982. Following the first IVF birth in Australia, the Government of Victoria established a review of IVF research and practice which led to the proclamation of the Infertility (Medical Procedures) Act 1984, the first legislation to regulate IVF and its associated human embryo research. Despite such restriction, IVF doctors and scientists from Victoria, especially those under the leadership of Carl Wood, Alan Trounson and Ian Johnston continued to initiate new treatments for infertility and new methods for delivering this treatment. In the USA IVF research began on animals as early as the 1930s, when Pincus and Enzmann at Harvard were involved in attempts at IVF in the rabbit. In the 1940s, John Rock attempted human IVF with 138 human oocytes without success. In 1965, Bob Edwards was with Georgeanna and Howard Jones at Johns Hopkins where attempts were made to fertilize oocytes in vitro. Clinical IVF began in earnest in the USA in 1980 with the first birth in 1981 achieved by the use of HMG--a first successful use with IVF. In France, two groups Frydman and Testart (Clamart) and Cohen, Mandelbaum and Plachot (Sevres) focused their research in particular directions. In 1981, the Clamart group developed a plasma assay for the initial rise in LH. The Sevres group developed a transport technique. Plachot produced a long series of cytogenetic analyses of oocytes and human embryos. Mandelbaum described the microstructures of the human oocyte. The start of IVF in France benefited from the help of animal researchers from the Institut National de la Recherche Agronomique. The first babies were born in Clamart in February 1982 and in Sèvres in June 1982. Important contributions to the development of IVF from the Nordic countries include techniques for ovarian stimulation, sonographic techniques for monitoring and vaginal oocyte retrieval and also unique possibilities for monitoring IVF safety. These developments, in combination with relatively permissive laws for the practice of reproductive medicine and relatively generous reimbursement policies, as well as a general public confidence in IVF, have led to an exceptionally high availability of IVF, within international comparison.

Purification of a candidate gonadotrophin surge attenuating factor from human follicular fluid

Gonadotrophin surge attenuating factor (GnSAF) is a new non-steroidal ovarian substance, different from inhibin, which attenuates the pre-ovulatory luteinizing hormone (LH) surge in superovulated women. Human follicular fluid (FF) was used as a source for the isolation of GnSAF, the activity of which was monitored in an in-vitro pituitary bioassay. Primary rat pituitary cells were incubated with test substances for 48 h and subsequently washed and incubated with 0.1 micromol/l gonadotrophin releasing hormone (GnRH) plus test substances for 4 h. GnSAF activity was expressed as the reduction of GnRH-induced LH secretion in the 4 h incubation. GnSAF was purified from 250 ml of FF which was heat-treated at 80 degrees C for 5 min. Heparin-sepharose chromatography, Con-A sepharose chromatography, reversed-phase high-performance liquid chromatography (HPLC) and preparative native gel electrophoresis were used for GnSAF fractionation. Using these purification steps, we have obtained an apparently homogeneous preparation that stains as a single band on sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis. GnSAF has an apparent molecular weight of 12.5 kDa and was identified by amino acid sequence (mass spectrometry) to be the C-terminal fragment of human serum albumin.

Development and application of competitive ELISA assays for rat LH and FSH

Rat LH (rLH) and FSH (rFSH) were measured by sensitive and specific competition ELISAs. The rat LH ELISA used rLH-I-9 coated plates, an antiserum against rLH and an antibody against rabbit IgG labeled with peroxidase. Using rLH-RP-3 as a standard, rat LH was determined by binding of the anti-LH antibody to rLH-I-9 coated plates. The sensitivity of the assay was 0.8 ng/mL. Similarly, the rat FSH-ELISA used rFSH-I-8 coated plates, an antiserum against rFSH and an antibody against rabbit IgG labeled with peroxidase. Using rFSH-RP-3 as a standard, the FSH-ELISA was also determined by binding of the anti-FSH antibody to rFSH-I-8 coated plates. The sensitivity of this assay was 1.25 ng/mL. Both rat LH and FSH ELISA assays are highly specific and provide accurate determination of gonadotrophins in buffers, sera, cell culture media, and anterior pituitary extracts. These assays were used for monitoring the gonadotrophin surge-attenuating factor (GnSAF) and inhibin activities present in human follicular fluid (hFF). The 2 new ELISA procedures have practical advantages (safety, convenience, economy) over the RIA methods, and they perform as well as the RIA techniques at the same range of concentrations.

Hypogonadotropic patients with ultrasonographically detected polycystic ovaries: endocrine response to pulsatile gonadotropin-releasing hormone

To characterize the endocrine response during induction of ovulation in patients with hypogonadotropic hypogonadism and ultrasound findings of polycystic ovary, we performed a retrospective analysis of 22 treatment cycles with pulsatile gonadotropin-releasing hormone (GnRH) in such patients and of 17 treatment cycles in similar patients with ultrasonographically normal ovaries. Of the 21 patients studies, 11 had an ultrasound finding of polycystic ovaries and ten had ovaries that appeared normal. Serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and estradiol levels, number of follicles of diameter > 12 mm (by ultrasound), and ovulation and conception rates were measured. Patients with hypogonadotropic hypogonadism and ultrasound-diagnosed polycystic ovary had pretreatment endocrine status similar to those with normal ovaries, but had much higher baseline ovarian volume. Ovulation induction with pulsatile GnRH induced much higher serum LH concentrations in the former group despite similar FSH levels. This difference preceded any change in estradiol levels. The former group consistently recruited significantly more follicles during pulsatile GnRH treatment. However, ovulation and conception rates were (non-significantly) higher in the latter group. In conclusion, this study characterized a subgroup of hypogonadotropic patients with ovarian morphology, volume and response to ovulation induction similar to in patients with polycystic ovary syndrome. When treated with pulsatile GnRH, those with polycystic ovary significantly hypersecreted LH before their estradiol level changed significantly. The primary lesion in polycystic ovary syndrome seems to be in the ovary, with pituitary hypersecretion of LH secondary to disturbed ovarian feedback signalling.

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.

Characterization of a rat anterior pituitary cell bioassay

We have described the protocols and characterization of a pituicyte culture, which became established as a reliable and reproducible bioassay for the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The bioassay was used to measure the bioactivity of factors that inhibit and stimulate gonadotrophin secretion. The protocol that was used involved the culling of female Wistar rats (200 to 250 g weight), at random stages of their cycle, and dispersal of their pituicytes in a concentration of 0.4 x 10(6) cells.ml-1.well-1 in serum-free medium (Dulbecco's modified Eagle's medium/Ham's F12 mixture, supplemented with insulin and transferrin) in Falcon 3047 24-well culture plates. After 24 h of pre-culture, the medium was changed and the cells cultured for a further 48 h. The supernatant was removed and assayed for basal secretion of FSH and LH. The cells were then stimulated with 10(-8) M GnRH for 4 h and the supernatant assayed for gonadotrophin-releasing hormone (GnRH)-stimulated FSH and LH secretion. All samples were assayed as pairs of duplicates (i.e. quadruplicate samples) which were randomly added to the plates to minimize plate effects. Random number tables were used to achieve this randomization.

Effects of FGA and PMSG on follicular growth and LH secretion in Suffolk ewes

The effects of fluorogestone acetate (FGA) and/or pregnant mare serum gonadotrophin (PMSG) on follicular growth and LH secretion in cyclic ewes were determined. Suffolk ewes (n=40), previously synchronized with cloprostenol were divided into 4 experimental groups (n=10 ewes per group). Group I served as the control, while groups II, III and IV received FGA, PMSG, FGA and PMSG respectively. Four ewes of each group underwent daily laparascopy for 17 d. All the ovarian follicles>or=2 mm were measured, and their relative locations were recorded on an ovarian map in order to follow the sequential development of each individual follicle. Comparisons were made of the mean day of emergence and the mean number of small, medium and large follicles, the atresia rate and the ovulation rate. For each group, 3 waves of follicular growth and atresia were observed during the cycle. During luteal phase, FGA treatment accelerated the mechanisms of follicular growth but reduced the number of large follicles and increased the atresia rate. In the follicular phase, FGA treatment was detrimental to both the number of large follicles and the ovulation rate. By contrast, PMSG enhanced recruitment of small follicles and the ovulation rate. Serial blood samples were collected during the luteal and follicular phases to study LH secretion. None of the treatments had any effect on LH secretion patterns.

The prognostic value of serum concentrations of progesterone, estradiol, and luteinizing hormone during superovulation with and without adjunctive leuprolide therapy

OBJECTIVE

To determine the predictive value of preovulatory serum concentrations of P, E2, and LH for pregnancy achieved with IUI after superovulation with and without adjunctive leuprolide acetate (LA) therapy.

DESIGN

Randomized, crossover study of superovulation with and without LA therapy.

SETTING

Infertility clinic.

PATIENTS

Subfertile patients referred for superovulation and IUI.

MAIN OUTCOME MEASURES

Preovulatory serum concentrations of P, E2, and LH on the day of hCG administration; pregnancy.

RESULTS

Preovulatory serum concentrations of P, E2, and LH had equivalent predictive value for pregnancy during cycles stimulated without LA therapy. No single parameter was particularly useful in clinical decision making. Threshold P concentrations proposed in other studies as useful in predicting pregnancy did not correlate with cycle fecundity. The predictive value of preovulatory concentrations of P during superovulation with adjunctive LA therapy was significantly worse than P concentrations during superovulation without LA therapy.

CONCLUSIONS

Preovulatory serum P, E2, and LH concentrations in superovulation and IUI are not helpful in determining prognosis for pregnancy. The relative utility of predictive parameters may vary for different treatment regimens.

Luteinizing hormone: its role, mechanism of action, and detrimental effects when hypersecreted during the follicular phase

OBJECTIVE

To review studies that have examined the role of LH, its mechanism of action, and its detrimental effects when hypersecreted during the follicular phase.

DESIGN

Important published studies related to this topic were identified through a computerized bibliographic search.

PATIENTS, PARTICIPANTS

Review of the need for LH during the follicular phase is based on animal models and women with hypogonadotropic hypogonadism. The association of hypersecretion of LH during the follicular phase with low rates of fertilization and high rates of pregnancy loss is based on clinical studies conducted in patients treated by IVF and ET and by induction of ovulation. The possible mechanism by which the effects occur is based on in vitro studies.

RESULTS

The results of the studies cited in this review are consistent with the two-cell two-gonadotropin hypothesis implying that synergistic action of both FSH and LH is required for appropriate steroidogenesis. It also seems that, whatever the underlying mechanism, a raised serum LH concentration during the follicular phase confers a substantial risk of infertility and early pregnancy loss.

CONCLUSION

By reviewing the literature it appears that LH exhibits an important role in the development of the growing follicle and maturation of the oocyte. It also seems that hypersecretion of LH during the follicular phase implies adverse effects on the fertility process. To further test this hypothesis, we now need systemic assessment of the methods of therapy used for treating patients with polycystic ovary syndrome, in relation to LH secretion and outcome of pregnancy.

Induction of ovulation for assisted reproduction programmes

The decision to use enhancement of the natural ovarian/menstrual cycle to attempt collection of several oocytes during IVF and GIFT cycles has dramatically increased the pregnancy rates. Furthermore, the recovery of multiple fertilizable oocytes allows for cryopreservation of extra or surplus pre-embryos (or embryos), with the consequent reduction in the risk of multiple pregnancies and the improvement of the cumulative pregnancy rate following IVF and GIFT cycles. Here, we have reviewed the underlying physiological mechanisms in the natural ovarian-menstrual cycle. Subsequently, we have analysed the more frequently utilized ovarian stimulatory regimens with special emphasis on the use of gonadotrophins. Several conclusions may be drawn from the experience to date with these methods of ovarian stimulation. Primarily, lower doses of medication, when used appropriately, may result in a more favourable outcome. Most significant, it seems to be beneficial to tailor the dosages and timing of drug administration to the patient's individual response to medication. Because ovarian stimulation therapy is difficult to manage, a major challenge in reproductive endocrinology has been to develop stimulation protocols that would 'ideally' synchronize the development of a cohort of follicles. The development of GnRH analogues (agonists and antagonists) and the experience (both in women and macaques) gained so far when these drugs are used in combination with gonadotrophins, have helped both in the understanding of the underlying physiology and in the improvement of clinical results.

Generation and characterization of monoclonal antibodies to prostate secretory protein

Monoclonal antibodies (MAbs) were produced against a highly purified preparation of prostate secretory protein (PSP) isolated from normal seminal plasma. Fifteen antibodies were selected for further evaluation based on their strong reactivity and specificity for PSP. All the MAbs had a specificity for prostate epithelial cells and none reacted to any of a variety of normal tissues as determined by immunoperoxidase staining. Six of the MAbs were selected for further immunohistochemical evaluation based on their ability to recognize different antigenic determinants. Using competitive binding immunoassays, a variety of overlapping specificities were observed with at least 2 distinct epitopes identified. Although some staining variability was noted, the 6 antibodies, in general, gave the same pattern of tissue reactivity. Both the normal prostate and the benign prostate hyperplastic ductal epithelial cells stained intensely, with 78 to 100% and 50-100% of the cells staining, respectively. The number and often the staining intensity of the tumor cells decreased as the tumor became more undifferentiated. Approximately 40 to 100% and 15 to 70% of the tumor cells stained in the moderately-differentiated and well-differentiated carcinoma tissues, respectively, whereas either no staining was observed or less than 20% of the tumor cells stained in the poorly-differentiated and undifferentiated tumors. Most of the metastatic prostate tumors showed either no staining or scattered staining in a few cells (i.e., less than 20%).

Premature luteinizing hormone surges in menopausal gonadotropin-stimulated cycles in monkeys: lack of initiation by progesterone

The occurrence of spontaneous luteinizing hormone (LH) surges in women receiving human menopausal gonadotropins (hMG) for in vitro fertilization-embryo transfer is a significant clinical problem. One hypothetical mechanism is that premature progesterone (P) secretion occurring in the high estradiol (E2) milieu produced by hMG triggers the spontaneous LH surge. To investigate this possibility, 11 rhesus and cynomolgus monkeys were stimulated with hMG. At maximal ovarian stimulation, monkeys were injected with 15 micrograms/kg P (n = 3), 30 micrograms/kg P (n = 3), or 1,000 IU human chorionic gonadotropin (hCG) (n = 5; controls). Blood for E2, P, and LH was drawn twice daily in the periovulatory period and daily before and after this period. Laparoscopy was performed after P or hCG injection. In the 6 monkeys receiving P, no LH surges were detected. Further, postinjection P profiles and laparoscopy showed no evidence of ovulation. Controls demonstrated laparoscopic and hormonal evidence of ovulation. These findings suggest that P does not trigger LH surges in hMG-stimulated cycles.

Contraceptive potential of RU 486 by ovulation inhibition: II. Suppression of pituitary gonadotropin secretion in vitro

That the antiprogestin RU 486 delays or inhibits the LH surge, and induces premature luteolysis in monkeys and women concurrent with a reduction in LH/FSH secretion has been reported. Whether this inhibition of gonadotropin release was a result of action at the hypothalamic and/or pituitary level is unknown. Here, we utilized a rat pituitary cell culture system to evaluate direct RU 486 actions on pituitary gonadotropin secretion in vitro. Cell cultures were primed with 10 nM estradiol for 48 h in order to maintain progesterone receptors. Basal and GnRH-induced secretion were evaluated after a 4-hour incubation period. The progesterone antagonist RU 486 inhibited GnRH-induced LH and FSH secretion in a dose-dependent manner, without affecting basal gonadotropin release. This inhibition of gonadotropin secretion was specific and antagonized by addition of progesterone in vitro.