The response of the pituitary-ovarian axis to pulsatile administration of gonadotropin-releasing hormone in long-term oral contraceptive users

OBJECTIVE

Our purpose was to differentiate between pituitary and hypothalamic feedback effects of oral contraceptives.

STUDY DESIGN

Twenty micrograms of gonadotropin-releasing hormone was administered intravenously at 90-minute intervals for 4 days to 14 long-term users of a combined oral contraceptive (30 micrograms of ethinyl estradiol and 150 micrograms of levonorgestrel), starting at different moments in the pill cycle. On the fourth day of administration the pulsatile release of luteinizing hormone was determined by blood sampling every 10 minutes for 6 hours. The sensitivity of the pituitary was determined before, during, and after treatment with gonadotropin-releasing hormone by a 100 micrograms gonadotropin-releasing hormone challenge test. On each sampling day serum estradiol, progesterone, and prolactin levels were measured, and ovarian ultrasonography was performed.

RESULTS

After 4 days of pulsatile gonadotropin-releasing hormone administration every exogenous gonadotropin-releasing hormone bolus was followed by an endogenous luteinizing hormone pulse of high amplitude (median 3.30 U/L). Both serum luteinizing hormone and follicle-stimulating hormone levels increased significantly (p < 0.001). The increase in follicle-stimulating hormone levels was accompanied by an increase in serum estradiol (p < 0.01). The luteinizing hormone response to a 100 micrograms bolus of gonadotropin-releasing hormone decreased during gonadotropin-releasing hormone treatment (p < 0.01), whereas the follicle-stimulating hormone response did not change.

CONCLUSION

Pituitary sensitivity is not impaired during oral contraceptive use, suggesting that oral contraceptives exert their negative feedback effects predominantly at the hypothalamic level.

Buserelin. A review of its pharmacodynamic and pharmacokinetic properties, and clinical profile

The gonadotrophin releasing hormone (GnRH) [luteinising hormone-releasing hormone (LHRH); gonadorelin] agonist buserelin is a promising new agent in the treatment of a variety of disorders in gynaecology and andrology, paediatrics and oncology. While a single dose of buserelin stimulates the release of pituitary gonadotrophins, multiple doses produce reversible pituitary desensitisation, and this specific blockade of gonadotrophin support to the gonads provides the basis for the drug's efficacy in conditions dependent on sex hormone secretion. Thus, buserelin provides comparable efficacy to orchidectomy or high dose estrogens in the treatment of hormone-sensitive prostate cancer and exhibits a lower incidence of adverse effects. During the early phase of treatment it may be particularly useful in combination with antiandrogens. Buserelin also appears promising in hormone-sensitive premenopausal breast cancer. Extensive studies have proven the value of buserelin in endometriosis, where it produces a transient remission with gradual recurrence of the disease on cessation of treatment. Surgical intervention is necessary in severe disease after buserelin-induced involution of the lesions. In patients with uterine leiomyoma, preliminary data suggest that buserelin may be beneficial in rendering surgery more conservative by reducing fibroid size, although it appears unlikely to preclude surgical intervention. The use of buserelin to induce a state of reversible hypogonadotrophism before administration of exogenous gonadotrophins is a promising strategy in the treatment of infertility associated with polycystic ovary syndrome and other conditions of infertility with underlying ovarian dysfunction; such a strategy also clearly enhances the efficiency of in vitro fertilisation programmes. Initial studies suggest its potential usefulness as a female contraceptive when administered intermittently in conjunction with a progestogen. Buserelin represents a first-line treatment of central precocious puberty. In endometriosis the adverse effect profile of buserelin is generally favourable, with hypoestrogenic effects such as hot flushes and vaginal dryness, and decreased libido, predominating. There is no apparent detrimental effect on lipid metabolism. The potential for adverse hypoestrogenic effects on bone mineral content with long term administration remains to be clarified. Thus, the GnRH agonist buserelin represents an advance in the treatment of a variety of gynaecological and andrological as well as paediatric and oncological conditions, infertility and other sex-hormone dependent conditions, with a low incidence of adverse treatment effects.

Endometrial histology during intermittent intranasal luteinizing hormone-releasing hormone (LH-RH) agonist sequentially combined with an oral progestogen as an antiovulatory contraceptive approach

Endometrial biopsies were performed in four groups of six or seven women treated for periods of 14 or 21 days with 200 micrograms twice daily or 400 micrograms once daily of intranasal Buserelin acetate. Five milligrams of medroxyprogesterone acetate (MPA) was taken orally twice daily on days 15 to 21. A medication-free week followed each treatment period. Between days 12 and 15 of the first treatment cycle, a proliferative endometrium was described in 16 out of 24 biopsies (66%). In 8 specimens (33%), early secretory changes were related to an early and/or short-lived rise in serum progesterone (P). At the end of the fourth treatment cycle, advanced maturation (days 23 to 28) was observed mainly in the 14-day schedules where serum estradiol (E2) was stimulated in or above the normal range of control cycles. Early to midluteal phase dating (days 16 to 22) was described mainly in the 21-day schedules. There was no P elevation in these groups. Five biopsies showing only proliferative tissue were associated with low levels of E2 mainly in the 400 micrograms/day group. The regimen capable of maintaining E2 in the low physiologic range (200 micrograms/12 hours X 21 days) was associated with incomplete secretory changes of the endometrium. A longer period of progestogen administration should produce a more complete maturation of the endometrium.

Endometrial morphology after 6 months of continuous treatment with a new gonadotropin-releasing hormone superagonist for contraception

Light and electron microscopic studies were performed on endometrial curettage specimens from 27 women after 6 months of contraceptive treatment with continuous intranasal gonadotropin hormone-releasing hormone (GnRH) superagonist. The GnRH superagonist nafarelin acetate (D-Nal[2]6-GnRH) was used in single daily doses of 125 or 250 micrograms. Ovulation was inhibited during all but one of the 159 treatment months. No pregnancies occurred. In 6 women with fairly regular bleedings, the endometrium displayed weak to normal proliferation. Twenty women developed oligomenorrhea or amenorrhea, 16 of them had inactive endometrium, 1 had weakly proliferative endometrium, and 3 endometrial biopsies were too sparse for adequate evaluation. One woman reported repeated episodes of heavy uterine bleedings. The endometrial biopsy from this woman showed weak proliferation. No signs of endometrial hyperplasia were observed. Generally, the electron microscopy showed signs of low metabolic activity and weak protein synthesis. Thus, long-term continuous treatment with nafarelin acetate for inhibition of ovulation does not appear to have untoward effects on the endometrium.

Pituitary response to LHRH in long-term users of injectable contraceptives

The site of gonadotrophin inhibition in long-term users of injectable contraceptives is still debatable. The pituitary response to LHRH (50 micrograms, I.V.) was assessed in 32 women. Sixteen cases were using either medroxyprogesterone acetate (DMPA; n = 8 150 mg I.M. every three months) or norethisterone enanthate (NET-EN; n = 8, 200 mg every 2 months) for at least 18 months. The remaining cases (n = 16) were normal fertile females not using any hormonal contraceptive (control group). The pituitary response to LHRH injection in both injectable subgroups was nearly identical to that in the control group. Neither the basal levels nor the net increase in gonadotrophins following LHRH injection were significantly different in the study groups from those of the control group. Long-term use of DMPA or NET-EN does not affect the pituitary responsiveness to LHRH injection and the pituitary is not a primary site for ovulation inhibition in these cases.

Fourteen-day versus twenty-one-day regimens of intermittent intranasal luteinizing hormone-releasing hormone agonist combined with an oral progestogen as antiovulatory contraceptive approach

This study was designed to determine the effect of discontinuous administration of a LHRH agonist on pituitary-ovarian function in normal women. The LHRH agonist buserelin (200 micrograms/12 h or 400 micrograms/24 h) was given intranasally for four consecutive cycles for 14 or 21 days in 26 normally cycling women. Five milligrams of medroxyprogesterone acetate were given orally twice daily from days 15-21. There was a 7-day pause between each medication cycle. Blood samples were drawn every other day for RIA of LH, FSH, estradiol (E2), and progesterone (P). Serum FSH increased for only a few days at the beginning of each cycle, whereas sustained elevation of serum LH occurred during LHRH agonist administration. Serum E2 increased rapidly and remained elevated during the administration of buserelin. Serum P remained in the follicular phase range or increased briefly after the initiation of buserelin occasionally in the 14-day regimens. After discontinuation of buserelin, E2 fell rapidly, and uterine withdrawal bleeding occurred. During the pause, FSH increased progressively. The patterns of gonadotropin response to buserelin were similar in the four cycles. Based on measurement of the areas of the response curves, serum LH and E2 levels were higher during the administration of 200 micrograms/12 h compared to 400 micrograms/24 h buserelin. However, down-regulation of the pituitary-ovarian axis, as evaluated by the acute gonadotropin response to buserelin on day 14, was more pronounced with 200 micrograms/12 h than with 400 micrograms/24 h. Breakthrough bleeding occurred in the 14-day schedules, whereas withdrawal bleeding occurred during the pause in the 21-day schedules. The immediate cycles following buserelin administration were normal ovulatory cycles. Intermittent LHRH agonist administration for 21 days avoided constant down-regulation of the pituitary-ovarian axis and allowed regular uterine bleeding. Combined with an appropriate P complement, it could be a useful contraceptive approach.

Single subcutaneous doses of a luteinizing hormone-releasing hormone antagonist suppress serum gonadotropin and testosterone levels in normal men

The ability of single doses of a LHRH antagonist [Ac-delta 3Pro1, 4F-D-Phe2, D-Trp3,6]LHRH (4F-antagonist) to suppress serum gonadotropin and testosterone levels was studied in six normal men. The 4F-antagonist was given sc at four doses: 40, 80, 160, and 320 micrograms/kg body weight. Serum immunoreactive LH, FSH, and testosterone and bioactive LH were measured at intervals for the subsequent 18 h. Serum LH decreased rapidly by (mean +/- SE) 39.7 +/- 2.7%, 41.6 +/- 5.4%, 45.5 +/- 4.7%, and 45.3 +/- 5.4% after each of the four doses. The mean number of LH pulses and their amplitude decreased after each dose and remained suppressed for at least 6 h. After each of the four doses, mean serum FSH levels decreased by 20.0 +/- 4.1%, 33.8 +/- 6.8%, 25.8 +/- 3.6%, and 33.3 +/- 5.7%, and mean serum testosterone levels decreased by 47.7 +/- 7.3%, 55.6 +/- 10.5%, 58.2 +/- 10.8%, and 76.0 +/- 6.0%. Serum testosterone remained low for at least 18 h after the two higher doses. LH bioactivity and the ratio of bioactive LH to immunoreactive LH decreased in all subjects, especially after higher doses of the 4F-antagonist. No side effects or adverse reactions occurred after 4F-antagonist administration, and toxicology studies were negative. These results demonstrate that a single sc injection of this potent LHRH antagonist inhibits the pituitary-gonadal axis in normal men.

Heterogeneity of sperm density profiles following 16-week therapy with continuous infusion of high-dose LHRH analog plus testosterone

LHRH agonist analogs have been investigated as potential male contraceptives. It has been shown that the LHRH agonistic analog [D-Trp6,Pro9-NEt] LHRH (LHRHA) given to men in single doses up to 500 micrograms daily for up to 20 weeks with the coadministration of testosterone enanthate produces reversible oligozoospermia. Individual responses to the treatment, however, were variable. In this study, we gave the same analog to eight normal male volunteers as a continuous infusion of 500 micrograms daily for 16 weeks. Testosterone enanthate, 100 mg, was given by injection every second week. Six of the subjects became oligozoospermic but the other two retained sperm counts that were greater than 20 million/ml, although their treatment continued for 20 weeks. The reasons for this variability of response are not clear. Serum immunoreactive LH values increased during the infusion period whereas testosterone declined. FSH values fell during treatment in all subjects except the two non-responders. The acute pituitary response to LHRHA during the treatment or shortly thereafter (48 h) was completely abolished, and bioactive LH values were suppressed totally. FSH, LH, testosterone and sperm counts returned to normal in all subjects following discontinuation of LHRHA infusion. Continuous infusion of 500 micrograms of LHRHA daily for 16 weeks with 100 mg of testosterone enanthate every 2 weeks induced desensitization of the pituitary, loss of LH bioactivity, and decreases of FSH and testosterone. This mode of administration, however, did not improve sperm density results obtained earlier by single daily injections of the analog. Heterogeneity of sperm density profiles still persists for reasons that are not yet clear.

Ovulation induction and pregnancy in women with hypothalamic amenorrhea treated with intermittent gonadotropin-releasing hormone

We induced ovulation in 34 cycles in 16 women following the administration of gonadotropin-releasing hormone (GnRH). In two patients two control cycles were induced. The patients self-administered GnRH through an indwelling intravenous catheter every 2 hours for 18 hours per day. In subsequent cycles the dose interval, dosage and infusion site, intravenous or subcutaneous, were varied. In all patients the estradiol, follicle-stimulating hormone and luteinizing hormone were measured, and follicular development was assessed ultrasonographically. Based on this preliminary study, a total of 34 cycles were studied in 16 women treated with 10 mg of self-administered GnRH intravenously every two hours during the day. Apparent ovulation was documented in all 34 cycles, and 11 pregnancies occurred. It appears that self-administered GnRH is economical and safe and achieves satisfactory results with respect to both ovulation and pregnancy.

Dose-related changes in LH bioactivity with intranasal GnRH agonist administration

In order to evaluate changes in bioactive (bio) and immunoreactive (i) LH and in FSH after intranasal administration of a GnRH agonist, two doses (125 micrograms and 250 micrograms) of nafarelin acetate were administered for 14 weeks to 7 normal women. Maximum changes in gonadotropins were observed 2-4 hours after both the first and last doses. However, the maximum acute responses of iLH, bioLH and FSH were significantly reduced after 14 weeks of treatment while no changes occurred in the bio: iLH ratio. The decrease in these acute responses were not dose-related. Serum iLH and FSH levels obtained prior to each dose (baseline) were not significantly altered by 14 weeks with either dose. However, baseline serum bioLH was significantly reduced compared to pretreatment by 14 weeks but only with the 250 micrograms dose (p less than 0.05). This level was also significantly different from the level of bioLH achieved with 125 micrograms (p less than 0.05). The bio: iLH ratio was also significantly decreased with the 250 micrograms dose. Although serum estradiol and progesterone levels suggested ovarian follicular activity and luteinization with the 125 micrograms dose, this did not occur with 250 micrograms of intranasal nafarelin. These data support a dose response effect of intranasal agonist treatment on the bioactivity of LH and also suggest the relevance of measurements of bioLH in assessing the effectiveness of agonist therapy.

Inhibition of ovulation during discontinuous intranasal luteinizing hormone-releasing hormone agonist dosing in combination with gestagen-induced bleeding

Four groups of eight or nine normal cycling volunteers with regular menstrual cycles had daily blood sampling during two pretreatment, two treatment, and two posttreatment cycles. Intranasal doses of 100, 200, and 300 micrograms of (D-Ser[TBU]6-des-Gly-NH210) luteinizing hormone-releasing hormone (LH-RH) ethylamide were administered every 12 hours and compared with a 400-micrograms dose given every 24 hours during two periods of 21 days followed by a drug-free interval of 7 days. Five milligrams of medroxyprogesterone acetate was taken orally on days 17 to 21. Serum luteinizing hormone was elevated during the first 2 weeks of treatment, and serum follicle-stimulating hormone was increased only during the first 2 days of treatment. At 100 to 300 micrograms/12 hours serum estradiol was stimulated up to preovulatory levels, whereas at 400 micrograms/24 hours most values were in the early follicular phase range. Ovarian ultrasonography revealed the transient development of preovulatory-like follicles in 8 of 12 studied cycles. Serum progesterone values were less than 2 ng/ml in 57.3%, between 2 and 5 ng/ml in 27.9%, and greater than 5 ng/ml in 14.7%. Withdrawal bleeding occurred during the pause in 97% of treatment cycles. Nine of 13 breakthrough bleedings happened in the groups given 100-micrograms and 300-micrograms/12 hours. Recovery cycles showed slightly prolonged follicular phases with normal luteal phases. No changes were observed in routine laboratory measurements. In conclusion, intermittent administration of appropriate LH-RH agonist dosing in combination with a progestogen would effectively block ovulation while preserving adequate cyclic estradiol secretion and could be an alternative contraceptive approach.

Inhibition of ovulation by intranasal nafarelin, a new superactive agonist of GnRH

Thirty healthy female volunteers used a new superactive stimulatory analog of the hypothalamic gonadotropin-releasing hormone (GnRH) for inhibition of ovulation and contraception during 3 months. The potent GnRH agonist nafarelin (D-Nal(2)6-GnRH) was administered intranasally in a daily dose of 125 micrograms to 15 women and 250 micrograms to 15 women. The treatment inhibited ovulation in all women during the 89 months of therapy. No pregnancies occurred during 59 treatment months in which no additional contraceptives were used. The mean estradiol concentration decreased during the 3-month treatment within the normal range for the early to mid-follicular phase of the menstrual cycle. The results suggest that the GnRH agonist nafarelin has a potential for contraception by inhibition of ovulation in women.

Contraception with an LHRH agonist: effect on gonadotrophin and steroid secretion patterns

Chronic treatment with the LHRH agonist D-Ser(TBU)6-LHRH (1-9)-EA (buserelin) has been suggested as a contraceptive method since it has been shown to inhibit ovulation. To elucidate the mechanism of this paradoxical action, we investigated the pattern of gonadotrophin and steroid secretion after the daily intranasal application of 300 micrograms of the agonist. Ten volunteers with ovulatory cycles received the analogue from Day 1 to Day 22 and 5 mg norethisterone acetate from Day 16 to Day 22. Blood samples were taken on Day 1, 15, and 21 every 15 min for 6 h after the application of the agonist. LH secretion was increased nine-fold on the first treatment day as compared to Day 2 of the preceding control cycle. Thereafter, it decreased slowly but was still elevated five-fold on Day 21 of treatment. FSH release increased three-fold on Day 1 but decreased thereafter to values similar to those of the controls. During treatment with the analogue, the LH/FSH ratio changed from 1.3 (controls) to 3.8 on Day 1 and to 5.5 on Day 15 and 21 of treatment. Although the ovary retained follicular activity, ovulation was inhibited in every treatment cycle. This seemed to be due to an impairment of follicular steroid synthesis as indicated by a significant increase of 17 alpha-hydroxyprogesterone and testosterone levels for several hours after the application of the analogue. It appears that at least during the first treatment cycle of daily administration of buserelin the abolishment of pulsatile gonadotrophin release, and the abnormally increased ratio of LH/FSH secretion may possibly impair follicular maturation and thus contribute to the inhibition of ovulation.

Sustained gonadal suppression in fertile women with the LHRH agonist buserelin

Nine fertile women were treated with the luteinizing- hormone-releasing hormone agonist buserelin (seven women received 800 micrograms, two women 1200 micrograms intranasally for up to 24 weeks). Both doses produced sustained suppression of ovarian function, accompanied by hot flushes. In five women chemical castration was established within 1 to 5 weeks, whereas in the other four volunteers transient peaks of serum oestradiol occurred between the 6th and 19th weeks. Thereafter low postmenopausal oestradiol levels persisted. Chemical castration was confirmed by hormonal parameters and endometrial biopsies (inactive endometrium). After cessation of treatment normal cyclical function occurred immediately. This reversible chemical castration may be useful for new therapeutical approaches in sexual hormone dependent diseases (endometriosis, precocious puberty, metastatic breast cancer).

Ultrasonic measurement of ovarian follicles during chronic LRH agonist treatment for contraception

Ultrasonic examinations of ovarian follicles were performed in seven healthy women on continuous luteinizing hormone-releasing hormone (LRH) agonist treatment for contraception. Four of the women had 1-4 uterine bleedings during the four-month study period and the remaining three women developed amenorrhea. The follicle diameter varied during LRH agonist treatment up to or above the preovulatory size of the normal menstrual cycle in the menstruating group of women. No ovulation occurred as judged by the low progesterone levels in serum. Slightly raised progesterone concentrations (mean 7.6 nmol/l) were observed during four treatment cycles with persistent follicles indicating luteinization of unruptured follicles. No or only small ovarian follicles (8-10 mm) were visualized by ultrasound in the amenorrheic group of women. This study further establish previous reports that chronic LRH agonist treatment effectively inhibits normal ovulation in regularly menstruating women.

Clinical applications of LHRH and its analogues

The physiological requirement for activation of pituitary gonadotrophin secretion by pulsatile LHRH stimulation is discussed, and compared with the effect of pituitary stimulation by LHRH agonists. Initial stimulation is followed by a phase of progressive pituitary and gonadal inhibition. This inhibition is fully reversible at the end of agonist treatment. Clinical applications of high dose suppression are the treatment of precocious puberty and hormone-dependent tumours (mammary and prostatic carcinoma). In women, agonist administration by nasal spray is a reversible method of inhibiting ovulation, and may also be useful in the treatment of endometriosis. Clinical advantages of agonist therapy are favourable biological tolerance, lack of side effects and rapid reversibility.

The effect of combined oral contraceptive steroids on the gonadotropin responses to LH-RH in lactating women with regular menstrual cycles resumed

The effect of combined oral contraceptive steroids upon pituitary response to stimulation with 100 micrograms LH-RH was studied in both non-puerperal and lactating women with regular menstrual cycles. Serum prolactin concentration was 14.20 ng/ml in non-puerperal women whereas it was 39.37 ng/ml in lactating women. A comparability was shown in the LH response to LH-RH in non-puerperal women and lactating women. FSH response to LH-RH, however, was significantly exaggerated in lactating-menstruating women as compared to that of non-puerperal women. Combined oral contraceptive steroids lowered basal levels of LH and FSH in non-puerperal women and lactating women although the difference was not statistically significant in non-puerperal women. The LH and FSH maximal responses to LH-RH were significantly diminished in both non-puerperal and lactating women on combined oral contraceptives. There was, however, no difference in the mean LH or FSH responses between non-puerperal women and lactating women. Combined oral contraceptive steroids used in this study seemed to suppress ovulation by decreasing the pituitary responsiveness to LH-RH in lactating-menstruating women as well as in normally menstruating women.

Failure to induce early abortion by huge doses of a superactive LRH agonist in women

The possible abortifacient effect of the potent stimulatory luteinizing hormone-releasing hormone analogue D-Ser(TBU)6-EA10-LRH was studied in five women in early pregnancy. Four of them were treated by intravenous injections of the superactive LRH agonist in a dose of 50-125 micrograms t.i.d. for four days (total dose 600-1500 micrograms). The fifth woman discontinued treatment after the first 50 micrograms dose. The treatment was instituted on gestational day 37, 38, 40, 42 and 46. Clinical examinations and frequently taken peripheral venous blood samples for analyses of human chorionic gonadotropin and ovarian steroids were used for monitoring the treatment. No abortifacient effects of these large doses of the superactive LRH agonist were observed and the pregnancies had to be terminated by suction curettage after 10-13 days. Thus, previously described luteolytic effects by superactive LRH agonist are overcome probably by endogenous chorionic gonadotropin in early human pregnancy.

Long-term intranasal luteinizing hormone-releasing hormone agonist treatment for contraception in women

Fifty-one female volunteers used a superactive stimulatory luteinizing hormone-releasing hormone (LH-RH) analog for suppression of ovulation for 3 to 12 months. The potent LH-RH agonist D-Ser(TBU)6-EA10-LH-RH was administered intranasally once daily in a dose of 400 or 600 micrograms. No pregnancies occurred during the 283 treatment months. Severe bleeding disturbances were not observed during the long-term treatment. No signs of hyperplastic changes were found in endometrial biopsies. There were no serious side effects. Ovulation promptly returned after cessation of treatment even in women with amenorrhea during treatment periods of 1 year or more. Thus, long-term LH-RH agonist treatment proved to be a safe, effective, and rapidly reversible new method for peptide contraception.

Induction of luteolysis by luteinizing hormone-releasing factor (LRF) agonist: sensitivity, reproducibility, and reversibility

The reproducibility, reversibility, and the maximal effectiveness of the luteolytic action of [D-Trp6,Pro9NEt]-LRF (luteinizing hormone-releasing factor) (LRF-agonist) were evaluated during 43 treatment cycles in 15 normal women. LRF-Ag (50 microgram) administration subcutaneously on 1 or 2 days at varying times during the luteal phase of consecutive cycles was made. Successful luteolysis was achieved in 26 of 27 cycles (96%) in which LRF-Ag was administered between 5 and 8 days after the luteinizing hormone (LH) peak. However, LRF-Ag treatment failed to induce luteolysis in 10 of 13 cycles (77%) when treatment began within 5 days of the LH peak. The luteal phase of posttreatment cycles was functionally unaffected by prior LRF-Ag treatment. The present study has thus demonstrated the reproducibility and reversibility of LRF-Ag as a potent luteolytic agent, although its action is dependent upon the timing of administration with a window of maximal effectiveness on days 5 to 8 of the luteal phase.

[The influence of long-term medication with the LH-RH analogue buserelin on the regulation of the menstrual cycle (author's transl)]

We investigated in 70 women over a period of 6 months the influence of different dose regimen of the potent LH-RH analogue Buserelin (HOE 766: 400, 200, 100 micrograms per day) on pituitary and ovarian function. The histological findings of the endometrial biopsy specimen (n = 109) were correlated with the hormonal profiles and the bleeding pattern. There was an evident dose-related inhibition of ovulation or corpus luteum integrity. A regular bleeding pattern was found more often in the lower dose groups. Unopposed estrogen effects recognized by prolonged endometrial stimulation were mainly registered in women with amenorrhea induced by 400 micrograms buserelin. Regression of endometrial stimulation could be observed during the six months period of medication. If higher dose regimen will lead to a more consistent inhibition of ovarian function, remains to be investigated.

Anovulatory effect of a LHRH antagonist in women

The antagonistic analog of LHRH, NAc-D-p-Cl-Phe(1),(2), D-Trp(3),D-Phe(6), D-Ala(10)-LHRH was administered intramuscularly in a dose of 2 mg to ten normally ovulating women on day 12 of the menstrual cycle. Ovulation was inhibited in six patients, and two more presented an insufficient corpus luteum. No pregnancies were recorded in this series. In those patients who did not ovulate, it was demonstrated that the LHRH analog abolished the midcycle surge of both LH and FSH. Luteolysis evidenced by the rapid decline in progesterone levels was present in 2 cases. Bleeding pattern showed a tendency to delayed menses. The morphological findings in endometrial biopsies of 6 women exhibited mild proliferation. Further research along these lines is necessary for appraisal of this approach to birth control.

Pituitary response to LHRH stimulation in women on oral contraceptives: a followup dose response study

Gonadotropic response to bolus intravenous injection of LHRH was measured in 36 women. Thirty of them were taking five different oral contraceptive preparations with six women in each category, and the remaining six served as controls. 150 micrograms LHRH was given during cycle days 20-25. Serum samples were obtained prior to the bolus injection and at 20 minute intervals for two hours. Five different oral contraceptive agents were selected to compare different progestins with same type and dose of estrogen, and different type or dose of estrogen with same type and dose of progestins. Significant suppression of LH response to LHRH stimulation ws observed in the agents containing 50 mcg of ethinyl estradiol or mestranol. No such suppression was noted in the product containing only 20 mcg of ethinyl estradiol. In comparing the different type of estrogenic or progestational components, no statistically significant differences in LH response were demonstrated. This finding suggests that it is not the individual component alone, but the combined action of estrogenic and progestational components which determines the potency of an oral contraceptive agent.

Endometrial patterns in women on chronic luteinizing hormone-releasing hormone agonist treatment for contraception

Endometrial biopsy specimens were obtained from 12 healthy women under chronic intranasal luteinizing hormone-releasing hormone (LH-RH) agonist treatment for evaluation of the risk of endometrial hyperplasia during long-term inhibition of ovulation. A single daily dose of 400 or 600 microgram of the superactive LH-RH agonist D-Ser(TBU)6-EA10-LH-RH was given for 13 to 55 weeks. Treatment was monitored by clinical examination, basal body temperature (BBT) recordings, and frequently taken venous blood specimens for determination of estradiol and progesterone. Ovulation was inhibited during all but 2 of the 102 treatment cycles. No pregnancy occurred. Six of the women had slight menstrual-like bleeding, and six hac amenorrhea during the treatment period. No dysfunctional uterine bleeding occurred. The dominating histologic picture of the 17 endometrial biopsies, obtained after 78 to 380 days of treatment, was inactive or weak proliferative glands with slightly atrophic stroma. There were no signs of hyperplasia. After discontinuation of treatment ovulatory menstrual cycle rapidly returned.

Failure to interrupt established pregnancy in humans by D-tryptophan-6-luteinizing hormone-releasing hormone

Four women 5 to 8 weeks into pregnancy, scheduled for therapeutic abortions, were given an analog of gonadotropin-releasing hormone, D-tryptophan-6-LHRH, in an effort to interrupt pregnancy. The treatment consisted of 100-micrograms injections, given twice daily for 5 to 10 days. No decline in serum beta-hCG or progesterone was noted, and menstrual extraction was needed in all women for pregnancy interruption. These data indicate that D-Trp-6-LHRH is not effective as an abortifacient in established pregnancy.

Combined use of clomiphene and intranasal luteinizing hormone-releasing hormone for induction of ovulation in chronically anovulatory women

Combined therapy with clomiphene and intranasal luteinizing hormone-releasing hormone (LHRH) was used to induce ovulation in eight chronically anovulatory patients under treatment for infertility. Clomiphene, 100 mg daily, was given from the 5th to the 9th day of the cycle. Synthetic LHRH was administered intranasally in different dosages from day 11 to day 14, in an attempt to induce late follicular development and ovulation. Five of the eight patients ovulated, and three conceived. The success achieved with combined clomiphene and intranasal LHRH administration suggests a therapeutic potential in the management of anovulatory infertility.

Luteolysis induced by a luteinizing hormone-releasing hormone agonist is prevented by human chorionic gonadotropin

The superactive stimulatory luteinizing hormone-releasing hormone (LRH) analogue D-Ser(TBU)6-EA10-LRh was administered intranasally to five healthy women in a daily dose of 600 microgram during two successive days of the mid-luteal phase. Both the basal serum progesterone levels and the length of the luteal phase were reduced, i.e. luteolysis occurred. Three women who were given additional treatment with human chorionic gonadotropin (HCG) in a daily intramuscular dose of 1500 IU for 10 days, had increased basal progesterone levels and a prolongation of the luteal phase. Thus, HCG prevented the luteolytic effect caused by the LRH agonist.

Ovulation inhibition by daily i.m. administration of a highly active LH-RH analog (d-ser(TBU)6-LH-RH-(1-9)-nonapeptide-ethylamide)

A highly active LH-RH-analog (D-Ser(TBU)6-LH-RH-(1-9)-nonapeptide-ethylamide = HOE 766) was administered to normally cyclic and ovulatory women in a double-blind study. Each woman received from day 1 through day 14 of the cycle according to a randomization plan either 10 microgram HOE 766 i.m. or a placebo. Ovulation was inhibited for at least two weeks in all subjects receiving HOE 766. The initially very marked release of LH measured 4 hourse after the injection decreased within 3 days by approximately 50%, and remained at this level for the remainder of the experiment while the initially high FSH response was abolished during further treatment. In 3 out of 5 women receiving the analog, serum estradiol was severely suppressed, in the remaining 2 slightly. Within 5 days after the discontinuation of treatment, the pituitary had regained the capacity to respond normally to LH-RH. It is postulated that follicular maturation is disturbed by the unphysiologic pattern of gonadotropin secretion during administration of HOE 766.

Pituitary and ovarian function in women receiving hormonal contraception

A study was performed to further evaluate pituitary-ovarian function in women receiving an oral contraceptive preparation. Basal hormone levels (follicle stimulating hormone, luteinizing hormone, estradiol and prolactin) and gonadotropic response to gonadotropic releasing hormone were studied in 12 healthy, regularly ovulating women in the early follicular and mid-luteal phases of their menstrual cycle (non-treatment control period). These same women were then given NORDETTE (ethinyl estradiol 30 microgram +d-Norgestrel 150 microgram) cyclically for 3 months. In the third month of treatment, the tests were repeated on day 21, i.e. after 21 active pills, and on day 28, i.e. after 21 active and 7 inactive tablets. On active preparation, basal luteinizing hormone, follicle stimulating hormone and estradiol and gonadotropin response to gonadotropin releasing hormone were significantly suppressed. However, by day 28 (after completion of the inactive tablets), basal gonadotropin and estradiol concentrations and the gonadotropic response to gonadotropic releasing hormone were not significantly different to their pretreatment levels. No consistent change in prolactin concentration occurred as a result of oral contraceptive therapy. These results indicate that the 'active' component of even a relatively low-dose pill causes considerable suppression of pituitary-ovarian function but that after 7 days of placebo, pituitary function and basal estradiol secretion have virtually returned to normal.

Restoration of the gonadotrophin response to LH-RH and oestrogen administration in patients after molar abortion

The relation of the hypothalamic-pituitary effect on gonadotrophin secretion and the concentration of serum hCG after molar abortion was investigated. Gonadotrophin release after a bolus injection of LH-RH or conjugated oestrogens was observed in 17 women until 5 months after molar abortion. Little if any response of gonadotrophin was observed at a hCG level of 100 mIU/ml or more, but the response of LH and FSH to LH-RH were restored to normal when the serum hCG level decreased to below 100 mIU/ml. A normal response of LH to conjugated oestrogens was observed at a serum hCG level of 20 mIU/ml or less. These findings suggest that a high level of hCG interferes with pituitary gonadotrophin secretion, that the threshold hCG levels for normal responses of gonadotrophins to LH-RH and oestrogen are 100 and 20 mIU/ml, respectively, and that secretion of gonadotrophins is restored even in the presence of a low hCG level.

Factors affecting pituitary gonadotropin function in users of oral contraceptive steroids

In order to determine whether certain factors influence the direct pituitary suppressive effect of contraceptive steroid, 50 subjects who had used various formulations of oral contraceptive steroids for periods of time ranging from one to nine years were stimulated with 50 microgram of gonadotropin-releasing hormone (GnRH) during the last week of oral contraceptive ingestion. The response of lutinizing hormone (LH) and follicle-stimulating hormone (FSH) was compared to the results obtained in nine control subjects with regard to: (1) age of subject. (2) type of contraceptive formulation used, and (3) length of use. Prestimulation levels of LH and FSH, respectively, were significantly decreased in 37 (74 per cent) and 42 (84 per cent) of the subjects. Following GnRH stimulation, peak responses of serum LH and FSH, respectively, were also significantly lower than those in the control subjects in 40 (80 per cent) and 45 (90 per cent of the subjects. The degree of suppression of pituitary gonadotropins, both before and after GnRH administration was significantly correlated with the type of steroid formulation used, being greatest with a combination of d-norgestrel and ethinyl estradiol. No correlation was found with length of use of oral contraceptives or age of the subjects.

Hypersensitivity of the human gonadotrophs to the repeated administration of small doses of LH-RH

The functional capacity of the gonadotrophs was assessed by repeated stimulation with small doses of LH-RH (5 microgram intravenously at 2-hour intervals for 3 injections) in normal women during the early and late follicular phases of the menstrual cycle. The results were compared to those obtained when a single dose (100 microgram) of the neurohormone was administered. During the early follicular phase, the release of LH and FSH remained about equal after the 3 successive injections of the small and after the large dose of LH-RH. During the late follicular phase, the release of LH and fsh increased progressively after the repeated administration of the 5 microgram of the neurohormone while the large dose induced a more pronounced and a more sustained pituitary response. This hypersensitivity of the gonadotrophs is observed when the E2 concentrations are higher than in the early follicular phase of the menstrual cycle.

Effects of aging on the hypothalamic-hypophyseal-gonadal axis in female rats

The failure of reproductive function in aged rats could be due to deficiencies at the level of the ovary, pituitary, hypothalamus, or higher brain centers. The classic explanation that the ovary is depleted of follicles does not receive adequate support on the basis of histologic studies of aged ovaries. Basal serum gonadotropin levels change with increasing age in female rats. Serum follicle-stimulating hormone (FSH) levels rise while serum luteinizing hormone (LH) levels fall. Likewise, the characteristic response to castration is markedly altered in aged female rats with a reduced secretion of FSH and a minimal elevation of LH. However, the pituitaires of these animals are still caapable of responding to exogenous LH-releasing hormone with a delayed LH response whose magnitude simulates that seen in younger female animals. With increasing age there is decreased pituitary and/or hypothalamic sensitivity to the feedback action of estradiol. These data are consistent with the postulation that there is an altered hypothalamic-hypophyseal function in aged rats.

Dynamic testing of hypothalamic-pituitary function in abnormalities of ovulation

A review of 26 unusual patients indicates that a combined luteinizing hormone-releasing hormone (LRH)-clomiphene test in conjunction with an estrogen provocation test not only was helpful in identifying underlying pathophysiology of anovulation but also proved useful in the clinical management of the patients. Dynamic testing per se does not establish a diagnosis but, in conjunction with history and other laboratory findings, it does make possible further subdivisions of groups of patients who otherwise appear similar, both clinically and from routine laboratory evaluations. It, therefore, tends to pinpoint a lesion and establish the area in which further tests should be made. It is concluded that the value of such investigations will be more evident as gynecologic endocrinology moves into investigation of the supratentorial control of hypothalamic function and as hypothalamic LRH becomes available as a therapeutic agent.

Luteinizing hormone-releasing hormone, ovariectomy, and silastic vaginal rings in the Rhesus monkey

The interaction of estradiol and luteinizing hormone-releasing hormone (LRH) may be a critical physiologic mechanism regulating the occurrence of ovulation in many species. These studies were conducted to assess (1) the effects of intramuscular injections of LRH in the intact female rhesus monkey and (2) the effects of estradiol in a Silastic delivery system in ovariectomized female rhesus monkeys. No changes in blood levels of luteinizing hormone (LH) were detected in response to 200 micrograms of LRH. Ovulation did not occur 48 hours after treatment. Ovariectomy decreased estradiol, increased LH, and had no effect on prolactin concentrations in sera. Insertion of a vaginal ring containing 10% estradiol increased blood estradiol levels 100-fold. Serum prolactin levels were unaffected; however, LH concentrations were altered in a multiphasic fashion. After the ring had been in place for 15 days, vaginal blood similar to menstrual flow was observed following removal.

Anterior pituitary sensitivity in immature female rats stimulated with gonadotrophin releasing hormone in vivo: effect of priming with oestrogen, pregnant mare serum gonadotrophin or brain lesion

An investigation of pituitary sensitivity, assessed in terms of increments in plasma LH and FSH concentrations, to stimulation with one or two injections of gonadotrophin releasing hormone (GnRH) was carried out on 26-day-old immature female rats which had received one of the following priming treatments: 10 μg oestradiol benzoate (OB) as a single injection on day 23 or day 25, or on both days; 10 i.u. pregnant mare serum gonadotrophin (PMSG) on day 24; an electrochemical brain lesion placed in the mediobasal hypothalamus on day 23; control animals received either vehicle alone or a sham lesion.

Pituitary sensitivity assessed at 10.00 h on day 26, after one or two injections of GnRH (100 ng/100 g body weight, s.c.), was enhanced to a similar degree in the three groups treated with OB in terms of LH (P < 0-01). The FSH response also increased after OB treatment but was not statistically significant. In contrast, 48 h after the injection of PMSG (i.e. when the rats were in a 'pro-oestrous-like' condition) pituitary sensitivity in terms of both LH and FSH dropped sharply (P < 0·001). In lesioned animals, pituitary sensitivity to one injection of GnRH was unchanged. A second GnRH injection administered after a 60 min interval induced a slightly larger LH response in control animals. In contrast, the ratio of the second response to the first increased in animals treated with PMSG, despite the state of overall decrease in sensitivity, being 4·5:1 in PMSG-treated rats versus 1·4:1 in controls.

In a second set of experiments, we investigated the variation of pituitary sensitivity in conjunction with an experimentally induced gonadotrophin surge. In animals treated with OB on day 23 and with 1 mg progesterone at 12·00 h on day 26, pituitary sensitivity was increased at both 14.00 and 17.00 h as compared with that in the day 23 OB-treated group at 10.00 h. The PMSG-treated animals maintained their state of decreased responsiveness at 14.00 h, but exhibited increased pituitary sensitivity at the time of the gonadotrophin surge (17.00 h).

These results show that OB increases pituitary sensitivity to GnRH in 26-day-old female rats and that the induction of a gonadotrophin surge further increases this sensitivity. In contrast, PMSG-treated rats displayed a state of decreased responsiveness 48 and 52 h, but not 55 h, after the injection. Pituitary sensitivity on the second day after PMSG treatment thus clearly differs from that observed during pro-oestrus in the adult cyclic female rat.

Control of ovulation and fixed time insemination in heifers following cloprostenol

The time of ovulation was determined in heifers following two injections 11 days apart of 500 microgram of cloprostenol by recovery of reproductive tracts at slaughter. Ovulation had not begun by 72 hours while 31%, 61% and 95% had ovulated by 78, 92 and 96 hours respectively after the second injection of cloprostenol. Injection of synthetic LH-releasing factor (GnRH) given 48 hours after cloprostenol significantly hastened the time of ovulation in animals slaughtered at 78 hours after the second cloprostenol injection. Insemination of heifers at 48, 60 or 72 hours resulted in lower fertility than two inseminations at 60 and 72 hours or at 48 and 72 hours after treatment. Controlling the time of ovulation with GnRH did not increase the fertility following a single insemination 71 hours after the treatment with cloprostenol.

Pituitary responses in LH secretion to LHRH during pregnancy

Thirty-six pregnant women and 15 normally menstruating women were each given 100 microng of synthetic luteinizing hormone releasing hormone (LHRH) by a single intravenous injection. Human chorionic gonadotropin (hCG), luteinizing hormone (LH), and follicle stimulating hormone (FSH) levels were determined by specific radioimmunoassay (RIA) technics. For the determination of the serum LH levels, the LHbeta-RIA method, which is unaffected by hCG at sample levels as high as 500 IU/ml, was used. Serum concentrations of LH and FSH were lower in pregnant women than in the normal women in the follicular and luteal phases. While the release of LH was observed in pregnant women following the administration of LHRH, the average net increase was less than that seen in both the follicular and luteal phases. During pregnancy, there was a progressive decrease in the LH response to LHRH, but no release of FSH.