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

Gonadotrophin regulation and clinical applications of GnRH

Gonadotrophin secretion is determined by the interplay of neural and gonadal influences. The neural influence is mediated for both LH and FSH by the decapeptide GnRH which is secreted into the hypophyseal portal vessels. LH is secreted in a pulsatile fashion apparently driven by episodic release of GnRH. Unremitting exposure of the pituitary to GnRH eventually abolishes gonadotrophin secretion. In primates, as opposed to the rat, GnRH appears to have a permissive role in the regulation of gonadotrophin secretion, priming the pituitary to secrete and show both negative and positive feedback responses to oestrogen in adult females. Striking physiological changes occur from fetal life to puberty in gonadotrophin regulation. GnRH acts on surface receptors. Chemical dissection of the GnRH molecule has disclosed a structure-activity relationship, allowing the development of both antagonist and 'superagonist' analogues. The initial stage in activation of gonadotrophs by GnRH appears to be binding to and clustering--probably dimerization--of GnRH receptors. Subsequent intracellular events are not fully clarified but grounds exist to suggest the involvement of both cyclic AMP and calcium fluxes within the cell. There is strong evidence that GnRH secretion influences the number of its own receptors in various situations in the rat. The phenomenon of pulsatile GnRH release in experimental animals survives hypothalamic deafferentation. Catecholamines are probably intimately involved in the generation of GnRH pulses--which for noradrenaline poses a paradox as all noradrenergic cell bodies lie outside the MBH. LH pulse frequency can be absent or altered in various states (e.g., Kallman's syndrome, hyperprolactinaemia and exposure to opiates--exogenous or apparently endogenous). The existence of GnRH receptors in gonadal tissue has been described but it is debatable whether this is true in man. Therapeutic uses of GnRH initially was aimed at correcting hypogonadotrophic hypogonadism. Development of GnRH superagonists demonstrated desensitization and thus their paradoxical application to the areas of contraception, precocious puberty and endocrine-dependent cancers. The development of miniaturized programmable infusion pumps has made pulsatile GnRH therapy a practical prospect. It holds considerable therapeutic promise in selected cases of hypogonadotrophic hypogonadism, especially in women.

Intranasal LHRH agonist treatment for inhibition of ovulation in women: clinical aspects

Daily intranasal administration of the potent stimulatory LHRH analogue D-Ser(TBU)6-EA10-LHRH was given to fifty healthy women for 3 months. Twenty-six women received 400 micrograms LHRH agonist/day and twenty-four women received 600 microgram/day. Inhibition of ovulation occurred during 147 of the 150 treatment months. The three presumptively ovulatory cycles were probably the result of initial technical problems with the nasal spray. No pregnancies occurred. Reactivation of corpus luteum with slightly raised progesterone levels in serum at initiation of treatment was observed in six women. During 20 month treatment the serum progesterone levels were slightly raised, indicating luteinization of follicles or defect luteal phases. Most of the women had menstrual-like bleeding during treatment. Seventeen volunteers had regular bleeding and twenty-three women had oligomenorrhoea. No dysfunctional uterine bleeding occurred, but three women reported spotting. The remaining ten women had amenorrhoea during treatment without any symptoms of oestrogen deficiency. After discontinuation of treatment the women regained ovulatory menstrual cycles after 31 days on average. The treatment was very well accepted by all the women.

Results of three-times-per-week long-term administration of a luteinizing hormone-releasing hormone (LHRH) analog, D-Ser-(TBU)6-LHRH-(EA)10 in primary amenorrhea

The effectiveness of a luteinizing hormone (LH)-releasing hormone (LHRH) analog, D-Ser-(TBU)6-LHRH-(EA)10 (Hoe 766), applied intranasally in a 3 days-per-week regimen, was assessed in four patients with hypogonadotropic or normogonadotropic primary amenorrhea by measuring LH, follicle-stimulating hormone (FSH), and estradiol (E2) levels before and 4 hours after its application and by observing the clinical effects of these hormones on the genital tract. The LH response increased progressively over the first 21 days (nine applications) in three of the four patients; it was subsequently reduced but never abolished throughout the study, which was terminated with the 25th application on the 59th day. Basal values of E2 increased until the 12th to 14th day (fifth or sixth application) and then showed a definite decline despite the continuing increase in LH response. FSH release attained a maximum by the second to fourth application and its magnitude of response remained remarkably stable thereafter. The clinical response did not correspond to the serum levels of E2. It is postulated that the development of LH unresponsiveness is due to desensitization of the receptors by the analog. The poor response of the genital tissues to the normal levels of E2 and the subsequent decrease in E2 levels, which occurred despite increasing LH responsiveness, are attributed to an inhibitory action of the analog on E2 biosynthesis in the ovary and on E2 receptors in the genital organs.

The biologic activity of a potent analogue of gonadotropin-releasing hormone in normal and hypogonadotropic men

We studied the biologic activity of a long-acting analogue of luteinizing hormone-releasing hormone, D-Trp6-Pro9-NEt-LHRH (LHRHa), in five normal men and four hypogonadotropic men previously unresponsive to natural LHRH. All subjects responded to LHRAa, but there were quantitative and qualitative differences between the normal and hypogonadotropic men. Normal men showed a linear dose-response relation, endogenous gonadal steroid secretion, and an adult pattern of gonadotropin secretion characterized by a high ratio of luteinizing hormone (LH) to follicle-stimulating hormone (FSH). Hypogonadotropic men had improving pituitary responses to each dose of LHRHa (priming response), no demonstrable gonadal steroid secretion, and a prepubertal pattern of gonadotropin release characterized by reversal of the normal ratio of LH to FSH. When compared with native LHRH, LHRHa had an augmented ability to discharge gonadotropins acutely and to sustain their release in normal and hypogonadotropic men.

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.