The role of the pituitary gonadotrophins in controlling luteal function in the stumptailed macaque has been investigated by examining profiles of serum concentrations of LH, FSH, progesterone and oestradiol in daily blood samples from 13 monkeys during the menstrual cycle, and in blood samples taken at hourly intervals between 09.00 and 21.00 h on different days of the luteal phase in 13 cycles. The effects of acute withdrawal of gonadotrophins was investigated by administering a single injection of 300 micrograms LHRH antagonist/kg body weight at different stages of the luteal phase during 28 cycles. Although there were high basal values and marked fluctuations of bioactive LH during the first 4 days after the LH peak, progesterone profiles showed no corresponding short-term changes, there being a slow and steady rise in progesterone concentrations during the sampling periods. After day 5, basal LH secretion decreased, but high amplitude LH pulses were identified which were associated with episodes of progesterone secretion. Administration of the LHRH antagonist caused a suppression of bioactive LH and progesterone concentrations at all stages of the luteal phase, although some basal secretion of progesterone was maintained through the 24-h period of effective antagonist gonadotroph blockade. Luteal function recovered apparently normally in all monkeys treated in the early-mid-luteal phase. Serum concentrations of FSH and oestradiol fluctuated comparatively less during the 12-h sampling periods, and the antagonist had less suppressive effects on the concentrations of these hormones. The LHRH antagonist had no apparent effect on prolactin release.(ABSTRACT TRUNCATED AT 250 WORDS)

Intermittent sc injection of a LHRH agonist reduced uterine fibroid size in 5 women. Commencement of the LHRH agonist buserelin on day 21 of the menstrual cycle induced a marked increase in plasma LH and FSH concentrations, followed by rises in estradiol (E2) and progesterone. LH and FSH levels fell to within the normal range by 120 h after beginning buserelin, despite continuing administration of the agonist. After menstruation, marked sustained suppression of cyclical gonadotropin and steroid concentrations occurred: mean values of FSH, LH, and E2 were 4.9 +/- 0.5 (+/- SE) mIU/ml, 5.9 +/- 0.6 mIU/ml, and 47.9 +/- 10.8 pg/ml, respectively, during the 20 weeks of buserelin treatment. During treatment, E2 concentrations remained below 50 pg/ml in 98 of 116 weekly observations. Uterine fibroids shrank after 8 or 10 weeks of buserelin administration, as assessed by ultrasound or gynecological examination. Compared to their initial volume, mean uterine fibroid volume after 20 weeks of buserelin infusion decreased from 220 +/- 51 to 98 +/- 26 cm3, which was 39.4 +/- 6.9% of the pretreatment volume. We conclude that sc administration of a LHRH agonist beginning in the luteal phase markedly reduced the size of uterine leiomyomata, suppressed, but did not abolish, pituitary and ovarian function, and warrants further evaluation as an option or adjunctive therapy to uterine myomectomy or hysterectomy.

Adult Soay rams were infused for 21 days with 50 \ g=m\ gbuserelin/day, using s.c. implanted osmotic mini-pumps. The continuous treatment with this LHRH agonist induced a supraphysiological increase in the blood concentrations of LH (15-fold) and testosterone (5-fold) followed by a decrease below pre-treatment values after 10 days. The blood concentrations of FSH showed only a minimal initial increase but the subsequent decrease was dramatic, occurring within 1 day. By Day 10 of treatment, the blood concentrations of all 3 hormones were low or declining, LH pulses were absent in the serial profiles based on 20-min blood samples and the administration of LHRH antiserum failed to affect the secretion of LH or testosterone. By Day 21, the secretion of FSH, LH and testosterone was maximally suppressed. The i.v. injection of 400 ng LHRH was totally ineffective at stimulating an increase in the blood concentrations of LH while the i.v. injection of 50 \ g=m\ g ovine LH induced a normal increase in the concentrations of testosterone; this confirmed that the chronic treatment with the LHRH agonist had desensitized the pituitary gonadotrophs without markedly affecting the responsiveness of the testicular Leydig cells. The ratio of bioactive:radioimmunoactive LH did not change during the treatment. The long-term effect of the infusion was fully reversible as shown by the increase in the blood concentrations of FSH, LH and testosterone and the return of normal pulsatile fluctuations in LH and testosterone within 7 days of the end of treatment.

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A dose of 100 \ g=m\ l of a potent ovine LHRH gamma globulin inhibited ovulation in the cyclic rat when administered at 12:00 h on the day of pro-oestrus. A dose of 10 ml of the preparation was administered i.v. to female stumptailed macaques to achieve circulating antibody titres 3\p=n-\4-fold higher than in the rat. In an ovariectomized macaque, this caused a marked fall in serum concentrations of LH to less than 10% of pretreatment values and also a significant, though less pronounced, fall in FSH. Six monkeys were treated with the LHRH gamma globulin during the mid\p=n-\latefollicular phase of the cycle. In 2 monkeys in which serum oestradiol concentrations were <100 pg/ml at the time of antibody administration, the rising oestradiol levels were abruptly suppressed and the normal mid-cycle LH surge failed to occur. Serum concentrations of LH and FSH declined to low levels for 8\p=n-\10 days after which time normal follicular development occurred. In the remaining 4 monkeys in which follicular development was more advanced as indicated by serum oestradiol concentrations of >100 pg/ml, the antibodies induced either a transient decline or had no effect on the rising serum concentration of oestradiol. An LH/FSH surge followed by a rise in serum progesterone occurred in these macaques. When the antibodies were administered to a further 6 macaques, which had also been treated with oestradiol benzoate during the early follicular phase to induce an LH surge, the neutralization of LHRH again failed to block the surge even when the dose of antibody was increased to 20 ml. The results show that LHRH antibodies were unable to block the LH surge in the macaque. They contrast with results obtained with LHRH immunoneutralization in the sheep, rat, hamster, mouse and bird and suggest that the ability of oestrogen to induce an LH surge by acting directly on the LHRH-primed anterior pituitary gland is more dominant in the primate.