Elevated FSH concentrations in imminent ovarian failure are associated with higher FSH and LH pulse amplitude and response to GnRH

Imminent ovarian failure (IOF) in women is characterized by regular menstrual cycles and elevated early follicular phase FSH. This study explored underlying neuroendocrine causes of elevated FSH concentrations on day 3 of the menstrual cycle. The characteristics of episodic secretion of FSH and LH, the pituitary response to gonadotrophin-releasing hormone (GnRH), plasma oestradiol, and dimeric inhibin A and inhibin B on day 3 were compared in 13 women with elevated FSH concentrations (>10 IU/l) and 16 controls. FSH amplitudes were higher in the IOF group than in the controls (P < 0. 0001). The FSH pulse frequency did not differ between groups. The FSH response to GnRH was higher in the IOF patients than in the controls (P < 0.0001). Mean LH, LH amplitude and LH response to GnRH were higher in the IOF group, but LH pulse frequency did not differ between the groups. Concentrations of inhibin A and inhibin B were lower in the IOF group, while oestradiol showed no differences. We concluded that in women with IOF, the pituitary is more sensitive to GnRH. This leads to higher FSH and LH pulse amplitudes which underlie the elevated FSH concentrations in the early follicular phase.     

Endocrinology: Evidence suggesting an additional control mechanism regulating episodic secretion of luteinzing hormone and follicle stimulating hormone in pre-pubertal children and post-menopausal women

The possible differential regulation of pulsatile follicle stimulatinghormone (FSH) and luteinizing hormone (LH) secretion in pre-pubertalchildren and in post-menopausal women was investigated. Childrenwere studied for 4 h and post-menopausal women for 6 h; bloodsamples were taken every 10 min. Post-menopausal women werestudied before and 21 days after administration of a singlei.m. dose of gonadotrophin-releasing hormone(GnRH) analogue.Eight post-menopausal women and 18 children (nine boys and ninegirls) were enrolled. The children were divided into two groups:A, at Tanner stages 0–1 (four boys and three girls); B,at Tanner stage 2–3 (five boys and six girls). PlasmaLH and FSH concentrations were determined using an immunofluorimetricassay. Time series were analysed and the specific concordance(SC) index was computed to determine the degree of concordancebetween episodes of LH and FSH secretion. While children ofgroup A had LH concentrations below the minimal detectable doseof 0.1 IU/I, group B showed measurable LH plasma concentrations(1.4 ± 0.3 IU/1, mean ± SEM). Plasma FSH concentrationswere detectable in both groups. Group A showed FSH plasma concentrationssignificantly lower than those of group B (0.75 ± 0.2and 1.95 ± 0.4 IU/1 respectively; P < 0.05), but FSHpulse frequency was higher in group A (P < 0.05). Childrenof group B showed significant concomitance of LH and FSH secretoryevents at time 0 (P < 0.05). Post-menopausal women showedboth LH and FSH plasma concentrations to be reduced after GnRHanalogue administration (P < 0.01), but only LH pulse frequency,not FSH pulse frequency, was significantly decreased (P <0.01). In these patients LH and FSH were co-secreted before(P < 0.05) but not after GnRH analogue administration. Inconclusion, this study confirms that during pre-puberty FSHis episodically secreted while LH is not. Following pubertaldevelopment, plasma LH concentrations increase and pulses ofthe two gonadotrophins are synchronized. The co-secretion ofLH and FSH is also observed in post-menopausal women, but notafter the single administration of a GnRH analogue. These datasuggest that FSH might have an additional stimulatory pathwaythat is independent of GnRH.     

Initiation of GnRH antagonist on Day 1 of stimulation as compared to the long agonist protocol in PCOS patients. A randomized controlled trial: effect on hormonal levels and follicular development

BACKGROUND The optimal time for GnRH antagonist initiation is still debatable. The purpose of the current randomized controlled trial is to provide endocrine and follicular data during ovarian stimulation for IVF in patients with polycystic ovarian syndrome (PCOS) treated either with a long GnRH agonist scheme or a fixed day-1 GnRH antagonist protocol. METHODS Randomized patients in both groups (antagonist: n = 26; long agonist: n = 52) received oral contraceptive pill treatment for three weeks and a starting dose of 150 IU of follitropin beta. The primary outcome was E(2) level on Day 5 of stimulation, while secondary outcomes were follicular development, LH during ovarian stimulation and progesterone levels. RESULTS Significantly more follicles on days 5, 7 and 8 of stimulation, significantly higher estradiol (E(2)) levels on days 1, 3, 5, 7 and 8 and significantly higher progesterone levels on days 1, 5 and 8 of stimulation were observed in the antagonist when compared with the agonist group. E(2) was approximately twice as high in the antagonist when compared with the agonist group on day 5 of stimulation (432 versus 204 pg ml(-1), P lt; 0.001). These differences were accompanied by significantly lower LH levels on days 3 and 5 and significantly higher LH levels on days 1, 7 and 8 of stimulation in the antagonist when compared with the agonist group. CONCLUSIONS In PCOS patients undergoing IVF, initiation of GnRH antagonist concomitantly with recombinant FSH is associated with an earlier follicular growth and a different hormonal environment during the follicular phase when compared with the long agonist protocol.     

Episodic leptin release is independent of luteinizing hormone secretion.

Several studies suggest that leptin modulates hypothalamic-pituitary-gonadal axis functions. Leptin may stimulate release of gonadotrophin releasing hormone (GnRH) from the hypothalamus and of gonadotrophins from the pituitary. A synchronicity of luteinizing hormone (LH) and leptin pulses has been described in healthy women and in patients with polycystic ovarian syndrome, suggesting that leptin may modulate the episodic secretion of LH. However, it has not been established whether LH regulates the episodic secretion of leptin. To further examine LH-leptin interactions, we studied the episodic fluctuations of circulating LH and leptin in two patients with Kallmann's syndrome (KS) before and on day 7 of pulsatile GnRH administration, and compared these with those observed in the early follicular phase of 10 regularly menstruating women divided into two control groups according to the body mass index of each patient. To assess episodic hormone secretion, blood samples were collected at 10 min intervals for 6 h, before and on day 7 of GnRH administration in KS patients, and during days 3-7 of the follicular phase in normally cycling women. LH and leptin concentrations were measured in all samples. For pulse analysis, the cluster algorithm was used. Before treatment, an apulsatile pattern with no endogenous LH pulsations was observed in both KS patients. However, leptin pulses were assessed in both women. During GnRH administration, pulsatile LH activity was achieved in both patients with pulse characteristics similar to those of the respective control group. Serum leptin concentrations and leptin pulsatile patterns were not modified. These results suggest that circulating leptin is probably not modulated by pulsatile GnRH-LH secretion.     

Phasic menstrual cycle effects on the control of breathing in healthy women

This study examined the effects of menstrual cycle phase on ventilatory control. Fourteen eumenorrheic women were studied in the early follicular (FP; 1-6 days) and mid-luteal (LP; 20-24 days) phase of the menstrual cycle. Blood for the determination of arterial PCO(2) (PaCO(2)) , plasma strong ion difference ([SID]), progesterone ([P(4)]), and 17beta-estradiol ([E(2)]) concentrations were obtained at rest. Subjects performed a CO(2) rebreathing procedure that included prior hyperventilation and maintenance of iso-oxia to evaluate central and peripheral chemoreflex, and nonchemoreflex drives to breathe. Resting PaCO(2) and [SID] were lower; minute ventilation (V (E)), [P(4)] and [E(2)] were higher in the LP versus FP. Within the LP, significant correlations were observed for PaCO(2) with [P(4)], [E(2)] and [SID]. Menstrual cycle phase had no effect on the threshold or sensitivity of the central and/or peripheral ventilatory chemoreflex response to CO(2). Both (V (E)) and the ventilatory response to hypocapnia (representing nonchemoreflex drives to breathe) were approximately 1L/min greater in the LP versus FP accounting for the reduction in PaCO(2) . These data support the hypothesis that phasic menstrual cycle changes in PaCO(2) may be due, at least in part, to the stimulatory effects of [P(4)], [E(2)] and [SID] on ventilatory drive.     

Induction of ovulation after gnRH antagonists

The gonadotrophin-releasing hormone (GnRH) antagonist binds competitively to the receptors and thereby prevents endogenous GnRH from exerting its stimulatory effect on the pituitary cells. This causes suppression of gonadotrophin secretion which occurs immediately after administration of the antagonist. When using GnRH antagonist in controlled ovarian stimulation, ovulation or maturation of the oocyte can, therefore, be induced by a variety of drugs, e.g. native GnRH, recombinant LH or short-acting GnRH agonists. Short-acting GnRH agonists were recommended for triggering ovulation in cases with a high risk of developing ovarian hyperstimulation syndrome (OHSS). Since it is evident that GnRH is required to initiate the LH surge and the oestradiol rise, a single administration of GnRH antagonist during the late follicular phase delays the LH surge. Studies showed that a single s.c. administration of 3 or 5 mg of Cetrorelix in the late follicular stage was sufficient to prevent the LH surge for 617 days. This phenomenon can be used in high responder patients who are prone to OHSS. The question whether this delay has any effect on oocyte quality and maturation still remains unanswered. Overall, there are four uses for GnRH antagonist: (i) using short-acting GnRH agonists for triggering ovulation in cases in which the GnRH antagonist is part of the protocol for ovarian stimulation. Recombinant LH and native LHRH could also be used as triggers of LH surge; (ii) delaying the LH surge in cases prone to OHSS by treatment with GnRH antagonist; (iii) to administer GnRH antagonist during the luteal phase to decrease the activity of corpora lutea; (iv) in polycystic ovarian disease with elevated LH the LH/FSH ratio can be corrected with the injection of GnRH antagonist prior to and during ovarian stimulation.     

Evidence of differential control of FSH and LH responses to GnRH by ovarian steroids in the luteal phase of the cycle

BACKGROUND: It is known that during the follicular phase of the cycle, estradiol sensitizes the pituitary to GnRH. The aim of this study was to determine the role of ovarian steroids in the control of GnRH-induced gonadotrophin secretion in the luteal phase of the cycle. METHODS: Eighteen normally cycling women were studied during the week following bilateral ovariectomy plus hysterectomy performed in early to mid-luteal phase. Six of the women received no hormonal treatment post-operatively (group 1, control), six received estradiol through skin patches (group 2) and the remaining six received estradiol plus progesterone (group 3). In all women the response at 30 min of LH (deltadeltaLH) and FSH (deltadeltaFSH) to GnRH (10 microg i.v.) was investigated on a daily basis. RESULTS: In group 1, serum FSH, LH and deltadeltaFSH values increased progressively following ovariectomy, while in groups 2 and 3 this increase was postponed or abolished. In contrast to deltadeltaFSH, deltadeltaLH values showed the same pattern of changes in all three groups with a significant decline up to post-operative day 4 and a gradual increase thereafter. CONCLUSIONS: These results demonstrate, for the first time, that in the early to mid-luteal phase of the cycle, estradiol and progesterone participate in the control of GnRH-induced FSH, but not LH, secretion. It is possible that in the luteal phase, the response of LH to GnRH is partly regulated by gonadotrophin surge attenuating factor.     

Controlled ovulation of the dominant follicle: a critical role for LH in the late follicular phase of the menstrual cycle

BACKGROUND: A method was sought to control ovulation of the dominant follicle and to test the importance of LH during the late follicular phase of the menstrual cycle. Menstrual cycles of rhesus monkeys were monitored, and treatment initiated at the late follicular phase (after dominant follicle selection, before ovulation). METHODS: The 2-day treatment consisted of GnRH antagonist plus either r-hFSH and r-hLH (1:1 or 2:1 dose ratio) or r-hFSH alone. In addition, half of the females received an ovulatory bolus of hCG. RESULTS: When treatment was initiated at estradiol levels >120 pg/ml, neither the endogenous LH surge, ovulation nor luteal function were controlled. However, when treatment was initiated at estradiol levels 80-120 pg/ml using either 1:1 or 2:1 dose ratios of FSH:LH, the LH surge was prevented, and ovulation occurred following hCG treatment. FSH-only treatment also prevented the LH surge, but follicle development appeared abnormal, and hCG failed to stimulate ovulation. CONCLUSIONS: Control over the naturally dominant follicle is possible during the late follicular phase using an abbreviated GnRH antagonist, FSH+LH protocol. This method offers a model to investigate periovulatory events and their regulation by gonadotrophins/local factors during the natural menstrual cycle in primates.     

Leptin concentrations in normal women following bilateral ovariectomy

To study the relationships between gonadal steroids and leptin, 20 women with normal cycles were investigated during the postoperative period following a laparotomy. Fourteen women underwent bilateral ovariectomy plus total hysterectomy either in the mid- to late follicular phase (n = 7, group 1) or in the early to midluteal phase (n = 7, group 2). The remaining six of the 20 women underwent cholocystectomy in the early to midfollicular phase of the cycle and were used as controls (group 3). In all three groups, serum leptin values decreased rapidly up to post-operative day 4. Then, leptin values increased significantly only in group 3 (P < 0.05). Leptin values before and after the operation showed significant positive correlations with body mass index (BMI), oestradiol and progesterone. However, with multiple regression analysis, BMI was the only parameter significantly correlated with leptin in group 3 (days 0 and 4-7), whereas in groups 1 and 2 progesterone and BMI showed independent significant correlations with leptin (days 0 and 8, r = 0.601 and r = 0.602 respectively). These results demonstrate for the first time a significant reduction in leptin concentrations in normal women following bilateral ovariectomy. Although BMI seems to be the predominant factor, it is also suggested that oestradiol and progesterone may participate in the control of leptin production during the human menstrual cycle.     

Luteinizing hormone response to gonadotrophin-releasing hormone in normal women undergoing ovulation induction with urinary or recombinant follicle stimulating hormone

Oestradiol enhances pituitary sensitivity to gonadotrophin-releasing hormone (GnRH) in normal women, while in women undergoing ovulation induction the putative factor gonadotrophin surge attenuating factor (GnSAF) attenuates the response of luteinizing hormone (LH) to GnRH. To study the relationships between oestradiol and GnSAF during ovulation induction, 15 normally ovulating women were investigated in an untreated spontaneous cycle (control, first cycle), in a cycle treated with daily i.m. injections of 225 IU urinary follicle-stimulating hormone (FSH) (Metrodin HP, uFSH cycle) and in a cycle treated with daily s.c. injections of 225 IU recombinant FSH (Gonal-F, rFSH cycle). Treatment with FSH started on cycle day 2. The women during the second and third cycle were allocated to the two treatments in an alternate way. One woman who became pregnant during the first treatment cycle (rFSH) was excluded from the study. In all cycles, an i.v. injection of 10 microg GnRH was given to the women (n = 14) daily from days 2-7 as well as from the day on which the leading follicle was 14 mm in diameter (day V) until mid-cycle (n = 7). The response of LH to GnRH at 30 min (deltaLH), representing pituitary sensitivity, was calculated. In the spontaneous (control) cycles, deltaLH values increased significantly only during the late follicular phase, i.e. from day V to mid-cycle, at which time they were correlated significantly with serum oestradiol values (r = 0.554, P < 0.01). Initially during the early follicular phase in the uFSH and the rFSH cycles, deltaLH values showed a significant decline which was not related to oestradiol (increased GnSAF bioactivity). Then, deltaLH values increased significantly on cycle day 7 and further on day v with no change thereafter up to mid- cycle. On these two days, deltaLH values were correlated significantly with serum oestradiol values (r = 0.587 and r = 0.652 respectively, P < 0.05). During the pre-ovulatory period, deltaLH values in the FSH cycles were significantly lower than in the spontaneous cycles. Significantly higher serum FSH values were achieved during treatment with uFSH than rFSH. However, serum values of oestradiol, immunoreactive inhibin, and deltaLH as well as the number of follicles > or = 12 mm in diameter did not differ significantly between the two FSH preparations. These results suggest that in women undergoing ovulation induction with FSH, oestradiol enhances pituitary sensitivity to GnRH, while GnSAF exerts antagonistic effects. The rFSH used in this study (Gonal-F) was at least as effective as the uFSH preparation (Metrodin-HP) in inducing multiple follicular maturation in normally cycling women.      

Follicular and luteal phase characteristics following early cessation of gonadotrophin-releasing hormone agonist during ovarian stimulation for in-vitro fertilization

Gonadotrophin-releasing hormone agonists (GnRHa) are widely used in in-vitro fertilization (IVF) for the prevention of a premature rise in luteinizing hormone (LH) concentrations. However, the administration of GnRHa during the follicular phase may also impair subsequent luteal function due to retarded recovery of pituitary gonadotrophin secretion. Therefore, luteal supplementation is generally applied. The present study was designed to determine whether a premature LH surge would still be prevented after early cessation of GnRHa during ovarian stimulation and whether subsequent luteal phase LH production would be sufficient to support progesterone synthesis by the corpus luteum. Sixty patients were randomized for three groups: (i) A long GnRHa/human menopausal gonadotrophin (HMG) protocol with luteal support by repeated human chorionic gonadotrophin (HCG) (n = 20), (ii) early follicular phase cessation of GnRHa without luteal support (n = 20), and (iii) a long GnRHa protocol without luteal support (n = 20). Frequent ultrasound and blood sampling was performed during the entire IVF cycle. Forty normo-ovulatory women served as controls. No premature LH surges were found after early cessation of GnRHa. In this group, some pituitary recovery occurred during the late luteal phase, but this did not affect corpus luteum function. Progesterone concentrations were shown to be dependent on disappearance of the pre-ovulatory bolus of HCG. Pregnancies occurred in all three groups. In conclusion, early follicular phase cessation of GnRHa is still effective in the prevention of a premature rise in LH. Although some pituitary recovery was observed thereafter, corpus luteum function is still abnormal due to early luteolysis.     

Endocrinology: Effect of mifepristone (RU486) on the pituitary response to gonadotrophin releasing hormone in women

Mifepristone interrupts folliculogenesis in women but the mechanismis not clear. Previous studies have investigated the effectof this compound on gonadotrophin secretion and have providedconflicting results. To study further the effect of mifepristoneon basal and gonadotrophin-releasing hormone (GnRH)-inducedgonadotrophin secretion, 12 normally ovulating women were investigatedduring two consecutive menstrual cycles, comprising an untreatedcycle (control) and a cycle treated with mifepristone. All womenwere treated with mifepristone on days 2–8 at the doseof 100 mg (group 1, eight women) or 10 mg per day (group 2,six women). Two women were treated with both regimens in twodifferent cycles. On day 8 of both cycles, the women receivedtwo GnRH pulses of 10 µg each 2 h apart. Blood samplesin relation to the first GnRH pulse were taken at –15,0, 30, 60, 120, 150, 180 and 240 min. In group 1, the increasein luteinizing hormone (LH) in response to GnRH was significantlyattenuated from 30 to 180 min, while the increase in folliclestimulating hormone (FSH) was attenuated only in response tothe second GnRH pulse. No significant decrease in LH and FSHresponse to GnRH was seen during treatment with the 10 mg dose(group 2). In group 1, serum oestradiol and inhibin-A concentrationsafter day 8 were lower than in the control cycles and the LHpeak was postponed by 7 days on average. Basal LH values increasedsignificantly on day 8 in both groups, while FSH values didnot change significantly compared with the control cycles. Asignificant increase in serum progesterone and cortisol valuesoccurred during the treatment only in group 1. Mid-luteal valuesof inhibin-A were significantly lower in cycles treated with100 mg mifepristone than in the control cycles. We concludethat the disruption of folliculogenesis by mifepristone cannotbe explained by a decrease in basal FSH concentrations duringthe critical period of follicle recruitment and selection. Itis possible that mifepristone exerts its effect at the levelof the ovary. It is also suggested that progesterone duringthe follicular phase of the cycle may participate in the controlof the self-priming action of GnRH on the pituitary.     

Utero-ovarian blood flow characteristics of pituitary desensitization

BACKGROUND: Down-regulation in assisted reproduction treatment cycles is monitored by suppression of ovarian/pituitary hormones and/or measurement of endometrial thickness. METHODS: This prospective longitudinal study reports on utero-ovarian characteristics of pituitary desensitization. A total of 75 patients were recruited; 32 had IVF treatment, 20 frozen--thawed embryo transfer cycles and 23 patients were recipients of donated oocytes. All received early follicular-phase down-regulation and had colour flow Doppler velocimetry of the utero-ovarian arteries < or =3 days before the start of menses and after 21 days of gonadotrophin-releasing hormone (GnRH) analogue treatment. Ovarian volume, endometrial thickness, pituitary and ovarian hormone concentrations were recorded at each scan. RESULTS: Significant changes (P < 0.05) were noted in these and utero-ovarian vasculature during the down-regulation period, with good correlation between resistance index and oestradiol estimations. Neither the type of GnRH analogue nor age influenced the changes in utero-ovarian blood flow. Ovarian artery resistance index was the best Doppler predictor for pituitary suppression and a mean discriminatory cut-off value of 0.867 +/- 0.025 was found to have the highest specificity and positive predictive value. CONCLUSIONS: This study has, for the first time, defined cut-off values for satisfactory pituitary suppression with high positive predictive value and specificity in an early follicular phase long protocol of GnRH analogue down-regulation using colour flow Doppler.     

Consequences on gonadotrophin secretion of an early discontinuation of gonadotrophin-releasing hormone agonist administration in short-term protocol for in-vitro fertilization

Administration of gonadotrophin-releasing hormone (GnRHa) agonists, used in IVF short-term protocols to initiate follicular recruitment, may be restricted to the early follicular phase without any further risk of LH surge. However, consequences of an early discontinuation upon residual endogenous gonadotrophin secretion are still unknown. Here, the effects of early cessation of GnRH agonist upon gonadotrophin secretion and ovarian parameters of IVF cycles were investigated. A total of 230 normo-ovulatory women were prospectively allocated to one of the two regimens: decapeptyl-GnRH (100 microgram) was daily injected either from day 1 to the triggering of ovulation (group 1) or for the first 7 days (group 2). Exogenous gonadotrophins (150 IU) were administered on day 4 and 5 with a subsequent adjustment. Detections of free alpha subunit and dimeric LH were performed by highly specific 'two site' monoclonal immunoradiometric assays. The results show that early discontinuation of GnRH agonist administration was associated with a sharp decrease in both plasma free alpha subunit and dimeric LH concentrations while plasma oestradiol response to exogenous gonadotrophins was reduced. Other ovarian parameters and pregnancy rate were unchanged. These data indicate that endogenous LH secretion is maintained by a daily administration of GnRH agonist and may contribute to the final follicular maturation.     

GnRH agonist as luteal phase support in assisted reproduction technique cycles: results of a pilot study

BACKGROUND: The aim of the study was to investigate whether intranasal (IN) administration of a GnRH agonist could provide luteal support in IVF/ICSI patients. METHODS: Controlled ovarian hyperstimulation (COH) was performed using hMG/FSH and a GnRH antagonist. Patients were then randomly allocated to either 10,000 IU hCG, followed by vaginal administration of micronized progesterone (3x 200 mg/day) (group A), or 200 microg IN buserelin followed by either 100 microg every 2 days (group B), or 100 microg every day (group C), or 100 microg twice a day (group D), or 100 microg three times a day (group E). Luteal support was continued for 15 days. RESULTS: Twenty-three patients were randomized. Groups B and C were discontinued prematurely in view of the short luteal phase. The luteal phase was significantly shorter in groups B, C and D, whereas group E was comparable with group A, 13.5 and 13.0 days, respectively. In the mid-luteal phase, median progesterone levels were significantly lower in groups B, C and D, whereas group E was comparable with group A, 68.9 and 98.0 ng/ml, respectively. Estradiol (E2) was significantly reduced in groups B and D but sustained in group E. In the hCG group, LH levels were undetectable (<0.1 IU/l), whereas LH was detectable and significantly higher in groups C, D and E. Two pregnancies were obtained in the hCG group (two of five), one ectopic and one ongoing. Three pregnancies were obtained in group E, one miscarriage and two ongoing twin pregnancies (three of five). CONCLUSION: IN administration of buserelin may be effective in triggering follicular maturation and providing luteal phase support in patients undergoing assisted reproduction techniques (ART).     

Role of gonadotrophin releasing hormone baseline concentrations in the control of pituitary gonadotrophin and ovarian steroid secretion in the pseudopregnant rat

To study the effect of moderately elevated gonadotrophin releasinghormone (GnRH) baseline concentrations during the luteal andthe follicular phase, pseudopregnant rats were infused s.c withGnRH at several doses for 5 days. These rats were also treatedwith oestradiol or sham-treated during the last 3 days of GnRHtreatment GnRH infusions started on day 7 or day 3 of the lutealphase of the ovulatory cycle; in the rat, the luteal phase orpseudopregnancy lasts about 10 days. Luteinizing hormone (LH)and follicle stimulating hormone (FSH) responses were inducedby i.v. injection of GnRH on day 12 (after expected luteolysis)or on day 8 (before expected luteolysis). In normal rats theLH and FSH responses induced by GnRH on day 12 were higher thanon day 8 (160 and 50% respectively). In GnRH-infused rats theLH and FSH responses were not increased. In these rats the lutealphase was extended (the plasma progesterone concentrations remainedhigh) and the onset of the follicular phase was postponed (plasmaoestrogen concentrations did not increase). Oestradiol increasedthe day 12 LH and FSH responses; this effect of oestradiol wassuppressed by GnRH infusion. On day 8, exogenous oestradiolalso increased the LH and FSH responses, but again the effectof oestradiol was suppressed when the animals were concomitantlyinfused with GnRH. These data may suggest that in the rat, GnRHbaseline concentrations participate in the neuroendocrine systemcontrolling gonadotrophin secretion and hence the ovulatorycycle.     

Analysis of hormonal changes during combined buserelin/HMG treatment

Changes of serum oestradiol, LH and progesterone have been analysed in view of the effect of the GnRH analogue buserelin on the late follicular and early luteal phase of cycles stimulated with combined buserelin/HMG (n = 31) in an IVF-ET/GIFT programme. Patients undergoing cycles with HMG only (n = 57) served as the control group. With the use of the GnRH analogue buserelin, a significantly higher amount of HMG (25 versus 20 ampoules; P less than 0.001) for a significantly longer stimulation period (10 versus 8 days; P less than 0.001) was necessary to achieve the same oestradiol response as seen in HMG cycles. Serum progesterone levels during a three day period before ovulation induction tended to be lower in the combined buserelin/HMG cycles than in cycles with HMG stimulation only. We did not observe any significant difference in the luteal phase progesterone levels of the buserelin/HMG and the HMG group. On the other hand, we found that an inadequate luteal phase in buserelin/HMG cycles could be avoided by HCG administration during the luteal phase. Both the elevation of basal serum LH and a premature LH rise could also be avoided by the use of buserelin.     

Ovarian feedback, mechanism of action and possible clinical implications

The secretion of gonadotrophins from the pituitary in women is under ovarian control via negative and positive feedback mechanisms. Steroidal and non-steroidal substances mediate the ovarian effects on the hypothalamic-pituitary system. During the follicular phase of the cycle, estradiol (E(2)) plays a key role, while circulating progesterone (at low concentrations) and inhibin B contribute to the control of LH and FSH secretion respectively. During the luteal phase, both E(2) and progesterone regulate secretion of the two gonadotrophins, while inhibin A plays a role in FSH secretion. The intercycle rise of FSH is related to changes in the levels of the steroidal and non-steroidal substances during the luteal-follicular transition. In terms of the positive feedback mechanism, E(2) is the main component sensitizing the pituitary to GnRH. Activity of a non-steroidal ovarian substance, named gonadotrophin surge-attenuating factor (GnSAF), has been detected after ovarian stimulation. It is hypothesized that GnSAF, by antagonizing the sensitizing effect of E(2) on the pituitary, regulates the amplitude of the endogenous LH surge at midcycle. Disturbances in the feedback mechanisms can occur in various abnormal conditions or after treatment with pharmaceutical compounds that interfere with the production or the action of endogenous hormones.     

Continuous administration of gonadotrophin-releasing hormone agonist during the luteal phase in IVF

BACKGROUND: It has been reported that ceasing the administration of gonadotrophin-releasing hormone (GnRH) agonist causes a profound suppression of circulating serum gonadotrophins. A comparative prospective and randomized study was conducted to investigate the effect of continuous administration of GnRH agonist during the luteal phase in an ovarian stimulation programme for IVF. METHODS: GnRH agonist was administered intranasally from the midluteal phase of the previous cycle, and pure FSH administration started on cycle day 7. In the continuous-long protocol (cL) group (n = 161 ), GnRH agonist administration was continued until 14 days after oocyte retrieval. In the long protocol (L) group (n = 158 ), GnRH agonist was administered until the day before human chorionic gonadotrophin (HCG) administration. RESULTS: The implantation rate and live birth rate per unit of transferred embryos were significantly higher in the cL group than the L group (P < 0.05 ). Serum LH and FSH concentrations on the day of, and 1 day after, HCG administration were significantly lower in the L group than the cL group (P < 0.01 ). CONCLUSIONS: Continuation of GnRH agonist administration during the luteal phase might facilitate implantation, and prevent the profound suppression of serum gonadotrophins.