Gonadotropin-releasing hormone: one polypeptide regulates secretion of luteinizing and follicle-stimulating hormones

Influence of LRH on gonadotrophin and testosterone levels in the foetal male rat

Gonadotrophin and testosterone levels were measured in male foetal rats at the 21st day of gestation 30 min following administration of LRH. The releasing hormone was administered by 3 different routes: subcutaneously as a single injection to the pregnant rat; subcutaneously as 12 times repeated injection to the pregnant rat from 16th-21st day of gestation; direct injection into the amniotic cavity. Three different doses of 1, 5, and 10 microgram/kg were used. The single administration to the dam was without effect. Repeated doses resulted in a significant dose-dependent elevation of mean foetal LH: 163 ng/ml in the control animals and 133,256, and 363 ng/ml in the 1, 5, and 10 microgram/kg LRH group resp. Intra animal injections significantly increased FSH and LH levels, but only those of FSH were clearly dose-dependent. A mean of 390 ng/ml in the control group was observed, with 1 microgram/kg LRH FSH was elevated to 723 ng/ml, at 5 microgram/kg to 928 and at 10 microgram/kg to 1017 ng/ml. Testosterone levels were not significantly altered. Our results demonstrate that the pituitary of foetal rats is able to respond to LRH in the same manner as adult animals.

Control of gonadotrophin secretion by steroid hormones in castrated male transsexuals. I. Effects of oestradiol infusion on plasma levels of follicle-stimulating hormone and luteinizing hormone

Twenty-four infusions of oestradiol (E2) in graded doses ranging from 0--200 micrograms administered over a period of 7 hours were carried out in eleven healthy male transsexuals who had undergone sex reassignment at least 3 months previously. Plasma levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and E2 were analysed by radioimmunoassay, while sex hormone binding globulin (SHBG) was measured using 3H-testosterone as the saturating ligand. Infusion of 5--200 micrograms of E2 raised plasma E2 to levels ranging from 38.4--367.8 pg/ml which present 83%--800% of levels found in a control group of sixty-three normal males. SHBG capacity remained unchanged at all doses of E2 studied. No change in plasma levels of FSH and LH was observed in control infusions and infusion of 5 micrograms of E2. From 10 micrograms-200 micrograms, suppression of plasma levels of FSH was noted at the 5--7 hour period. The suppression increased up to 20 micrograms and thereafter the levels of FSH remained constant. On the other hand, the suppression of LH increased up to the highest E2 dose (200 micrograms) studied. Further, significant suppression of LH occurred earlier than the 5--7 hours as the dose of E2 increased. These observations are consistent with the conclusions that: (1) E2 plays a part in the regulation of secretion of FSH and LH in men; and (2) at doses higher than physiological, E2 exerts a differential effect on the secretion of FSH and LH.

Chronic effects of the stimulatory luteinizing hormone-releasing hormone analogue D-Ser (TBU) 6-EA 10-LRH on the gonadotrophin and gonadal steroid secretion in women with amenorrhoea

The agonistic analogue of luteinizing hormone-releasing hormone (LRH) D-Ser-(TBU) 6-EA10-LRH was given subcutaneously or intranasally to 21 women with longstanding secondary amenorrhoea in an attempt to induce follicular maturation and ovulation. Seven women were given daily subcutaneous injections of 10 /micrograms of the LRH analogue for 21 days. The pituitary and ovarian responses were monitored by follicle-stimulating hormone (FSH), luteinizing hormone (LH), oestradiol (E2) and progesterone (P) in serum. A significant increase of the E2 levels in blood was seen during the first three days of treatment but the E2 elevations were not sustained. No signs of follicular maturation were detected during the treatment. Intranasal treatment with the LRH agonist was instituted in 14 women. Repeated daily low intranasal spray doses (1 - 10 /micrograms) were given. The treatment was continued for 2 - 4 weeks. Intranasal doses of 5 /micrograms and below were ineffective in increasing gonadotrophin and gonadal steroid secretion. An initial gonadotrophin release was observed after intranasal doses of 10 /micrograms and there was a slight increase of the E2 concentrations in serum during the first 2 - 3 days. The pituitary responsiveness to the agonist then decreased markedly during the treatment. None of the 14 women showed signs of follicular maturation during or after the treatment. The pituitary desensitization caused by this potent agonistic LRH analogue seems to limit its therapeutic use for treatment of anovulatory infertility.

[Diagnostic procedures in diencephalo-hypophyseal insufficiency (author's transl)]

A functional diagnosis of the diencephalohypophyseal system was carried out in patients with Sheehan syndrome, chromophobic adenoma, craniopharyngioma, prolactin-producing pituitary tumours, acromegaly, hypothalamo-pituitary dwarfism and constitutional retardation. A combined insulin hypoglycaemia/LH-RH/TSH test was performed to define frequency and extent of anterior pituitary insufficiency. With these illnesses, almost generally, a somatotropic insufficiency (except in acromegaly) was found. An impairment of gonadotropic function was often present, in general a pathologic LH-RH test correlating with a more or less developed androgen deficiency. An adrenocorticotropic insufficiency was found in most patients with sheehan syndrome, chromophobic adenoma and craniopharyngioma while in acromegaly and hypothalamo-pituitary dwarfism it was present less frequently, necessitating a substitution with corticoids. The TRH test reflects only incompletely a secondary hypothyroidism, and can be normal with organic processes of the diencephalo-hypophyseal region, making a T3 and T4 estimation in the blood decisive for a thyroid hormone substitution. A clear-cut separation of the hypothalamic from the pituitary cause of the insufficiency is neither possible with the LH-RH nor with the TRH test.

[Human prolactin (author's transl)]

Human prolactin (hPRL) is the most recent anterior pituitary hormone in human endocrinology, whose structure has been elucidated in 1977. The possibility to measure hPRL in serum has led to a rapid increase of our knowledge of prolactin-physiology and -pathophysiology in men. hPRL is the only anterior pituitary hormone which is under predominantly inhibitory hypothalamic control. The effects of prolactin in the various species differ considerably, whereas in men it acts mainly upon the mammary gland and the gonadal system. Hyperprolactinemia leads typically to hypogonadism, amenorrhea and frequently galactorrhea. The hyperprolactinemia-hypogonadism-syndrome has been identified as a separate entity in recent years. Because of the relative frequency of this disease prolactin measurements have become of great importance in the diagnosis of sterility. Depending on the cause of hyperprolactinemia a neurosurgical, radiotherapeutical or medical treatment is indicated.

Measurement of gonadotrophins, testosterone, delta4 androstenedione and dihydrotesterone in idiopathic oligospermia

Basal concentrations of FSH, LH, testosterone, delta4 androstenedione and dihydrotestosterone, together with FSH and LH responses to single injections of LHRH were determined in eighty-four patients with oligospermia and in twenty-seven normal men. LHRH responses were heterogeneous and indicate that various disorders might cause this syndrome. In six cases there appeared to be an isolated deficiency in spermatogenesis, as indicated by an increased FSH response, whilst the LH response was normal as were the concentrations of the testicular hormones. In twenty cases a concomitant disorder of Leydig cell function and spermatogenesis is suggested as indicated by increased FSH and LH responses and decreased concentrations of testosterone and delta4 androstenedione (six) or concentrations at the lower limit of normal (fourteen). Furthermore, in five cases a hypothalamic and/or pituitary disturbance may be accepted on the basis of normal or decreased basal concentrations decreased and responses to LHRH with decreased concentrations of testosterone and delta4 androstenedione. Finally, in thirty-seven cases, oligospermia was not associated with any modification basal gonadotrophin concentrations or response to LHRH when compared with normal subjects.

[Comparative studies of growth hormone secretion in acromegaly after isolated and combined application of insulin hypoglycemia, LH-RH- and TRH tests (author's transl)]

Growth hormone (GH) release was measured in 17 patients with active acromegaly following the administration of insulin, LH-RH and TRH given intravenously either combined or each separately. The simultaneous application of insulin and the hypothalamic releasing hormones resulted in a striking increase of plasma GH in 15 out of 17 patients. Inappropriate stimulation of GH release was found in 9 out of the 17 patients with acromegaly, when TRH was given as the only hormone; conversely this phenomenon due to LH-RH application was observed in 4 cases. In insulin-induced hypoglycemia GH release could be stimulated in 5 patients. After selective, transsphenoidal hypophysectomy, 4 of 13 patients still showed a definite stimulation of GH release after the combined use of test substances. Two of these also exhibited a comparable stimulation of GH after TRH, indicating adenoma cells remaining active after operation. The combined insulin-induced hypoglycemia/LH-RH/TRH-test is therefore advisable for patients with acromegaly, since GH release as well as other hypophyseal partial functions can be tested. The performance of individual tests is essential for evaluating selective stimulation of GH release.

Stimulation of luteinizing hormone (LH) and follicle-stimulating hormone by (D-Leu6, des-Gly10-NH2)-LH-releasing hormone ethylamide after subcutaneous, intravaginal, and intrarectal administration to women

Women, most of whom had regular menstrual cycles, were administered D-Leu6,des-Gly10-NH2)-luteinizing hormone-releasing hormone (LH-RH) ethylamide (D-Leu6-LH-RH-EA)via different routes during the early or midfollicular phase of the cycle. Plasma LH, follicle-stimulating hormone (FSH), and estrogen levels were determined by radioimmunoassay before and after administration of D-Leu6-LH-RH-EA. plasma LH and FSH increased and reached peak levels 3 to 4 hours and 3 to 6 hours, respectively, after subcutaneous injection of 25 mug of the analog of LH-RH. Intravaginal or intrarectal application of 2 mg of D-Leu6-LH-RH-EA also increased plasma LH and FSH levels in most of the women, but the magnitude of the rise, the time of initiation of response, and the peak level varied among the women. The plasma estrogen level also rose after administration via either route.

Acute effects of a new stimulatory luteinizing hormone-releasing hormone analogue D-Ser(TBU)(6)-EA(10)-LRH on the gonadotrophin and gonadal steroid secretion in women with amenorrhoea

A new stimulatory luteinizing hormone-releasing hormone (LRH) analogue D-Ser(TBU)(6)-EA(10)-LRH was administered subcutaneously in a dose of 10 microg into 10 women with amenorrhoea. The injection resulted in a 20-fold increase of the LH level in blood and a 5-fold increase of the FSH level with maxima at 4 and 6 h after the administration, respectively. There was an evident biphasic pattern of LH release similar to that described after extended pituitary stimulation by constant infusions of LRH with early and late peaks of LH combined with a gradual, progressive FSH release. The duration of the effect on LH and FSH was at least 12 and 24 h, respectively. All the women responded with evident oestradiol increases in blood during the last 18 h of the 24 h study period. A comparison between the effects of a single subcutaneous injection of 10 microg of the LRH analogue and 500 microg of LRH showed that the initial FSH and LH release was similar. However, the FSH and LH release during the remainder of the study period was significantly greater after administration of the analogue and so was the oestradiol increase. Thus, this study in women confirms previous studies in men that D-Ser(TBU)(6)-EA(10)-LRH is a potent stimulatory LRH analogue with prolonged biological activity.

Effects of a luteinizing hormone-releasing hormone analog on mating and fertility in rats

A rhythmic antifertility effect of a luteinizing hormone-releasing hormone (LH-RH) analog, [D-Ala6-des-Gly-NH210]-LH-RH-ethylamide (AY-25,205), administered intramuscularly every 3rd day staring in the afternoon of diestrus, was demonstrated in 4-day cyclic rats. The antifertility effect was achieved for a period of approximately four cycles when the females were allowed constant cohabitation with fertile males except for 24 hours following treatment. Unrestricted cohabitation resulted in some matings and pregnancies in the group treated every 3rd day and also in some of the groups treated every 4th day with restricted cohabitation. The antifertility effect of AY-25,205, with unrestricted cohabitation, disappeared when the second treatment was given 4 days after the first. It is presumed that the antifertility effect of AY-25,205 was achieved through its capacity to induce ovulation at a physiologically "wrong time" (i.e., 1 day before the expected day of proestrus) and through its effect on mating behavior. The present experimental models suggest that AY-25,205 or similar analogs could be potentially useful for a more reliable rhythm method of birth control in humans, by timing ovulation and narrowing the fertile period of the cycle.

Prostaglandins, possible mediators of the effects of oestrogens on luteinizing hormone output

A possible mechanism for the positive and negative feed-back effects of oestrogen on luteinizing hormone (LH) output is suggested. It is proposed that oestrogens may influence prostaglandin synthesis in the hypothalamus in relation to LH releasing hormone (LH.RH) synthesis and release. Changes in oestrogen level or in the oestrogen to progesterone ratio may alter the ratios of prostaglandin concentrations in the hypothalamus, and so modulate LH.RH output through effects on sympathetic neurotransmission, protein synthesis or LH.RH release.

Conformational flexibility of luteinizing hormone-releasing hormone in aqueous solution. A carbon-13 spin-lattice relaxation time study

The carbon-13 nuclear magnetic resonance (13C NMR) spectra of luteinizing hormone-releasing hormone (LH-RH) and lower homologous peptides have been assigned in aqueous solutions at various pH values. 13C spin-lattice relaxation times (T1) have been measured for all proton-bearing carbons at 25.2 and 67.9 MHz. From the T1 data the rates of overall molecular motion and intramolecular motion of side chains have been estimated. LH-RH is a flexible molecule in solution, having segmental motion along the backbone as well as in the nonaromatic side chains.

Use of synthetic luteinizing hormone-releasing hormone in treatment of oligospermic men: a preliminary report

Synthetic luteinizing hormone-releasing hormone (LH-RH) was administered to four normogonadotropic, oligospermic men (24 to 39 years of age) who had no endocrinologic, urologic, or associated vascular disease, to assess its possible therapeutic value in male infertility. Previous testicular biopsies of these subjects indicated alteration of spermiogenesis only. LH-RH (mean dose, 500 mug/day) was administered intramuscularly for 100 to 135 days. Each patient had at least two sperm count before starting therapy and had one every 20 to 30 days during and for two to five months after treatment. The sperm count, semen volume, sperm motility and morphology, and seminal plasma concentrations of fructose and citric acid were studied in each semen sample. In three of the four patients, urinary LH and FSH excretion and plasma testosterone levels were also measured. The sperm count increased clearly in two subjects 30 to 80 days after therapy started; the response was small in the third subject and negative in the fourth. The remaining parameters followed variable courses. Libido increased in all subjects. In the post-treatment period, the two patients who had shown the best response during treatment experienced a new and abrupt increase in the sperm count which remained well above initial values at the end of follow-up. LH-RH appears to be of value in the treatment of certain types of oligospermia, but several issues remain unsettled.

Prostaglandins in reproductive physiology

The role of prostaglandins in reproductive physiology is reviewed with particular emphasis on their possible importance in ovulation in humans. A possible interaction between gonadal steroids, biogenic amines and prostaglandins at hypothalamic-pituitary level, in relation to the release of luteinizing hormone releasing factor, and LH, is discussed. Anomalies regarding the role of oestrogens in LH release are noted, and it is suggested that high oestrogen levels may release prostaglandins from the uterus and/or centrally in humans, in connection with the mid-cycle LH surge and ovulation. A hypothetical role for prostaglandins in sexual behaviour and premenstrual changes is discussed.

The hypotheses open up new areas for clinical research to establish the role of prostaglandins in human endocrinology. The need for measurement of prostaglandin metabolites in blood and urine is emphasized.

Restoration of normal pituitary gonadotropin reserve by administration of luteinizing-hormone-releasing hormone in patients with hypogonadotropic hypogonadism

To elucidate whether diminished pituitary gonadotropin reserve can be restored by repeated stimulation with luteinizing-hormone-releasing hormone, plasma luteinizing hormone and follicly-stimulating hormone responses were studied before and after daily intravenous infusion of 400 mug of luteinizing-hormone-releasing hormone for two to 23 days, in patients with hypogonadotropic hypogonadism of various causes. In five of nine patients with isolated gonadotropin deficiency, the impaired plasma luteinizing hormone response was restored to normal after treatment for seven days or more, whereas it was unchanged in four patients treated for less than five days. However, six patients with anorexia nervosa regained normal responses after three to five days' treatment. Five of nine patients with organic hypothalamopituitary lesions also showed normal responsiveness after five to seven days' treatment. These results suggest that the response to the test after repeated administration of luteinizing-hormone-releasing hormone is of value for the diagnosis of hypogonadism of hypothalamic origin.