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

Induction of ovulation with synthetic gonadotrophin-releasing hormone in women with constant anovulation induced by contraceptive steroids

The ovarian response to stimulation with follicle-stimulating hormone/luteinizing hormone-releasing hormone (FSH/LH-RH) was studied in young, healthy, and fertile women with constant iatrogenic anovulation caused by depot medroxyprogesterone acetate or depot chlormadinone acetate injected for contraceptive purposes. Results were compared with those in unstimulated controls. The response was observed directly on the ovaries at laparotomy performed after treatment with FSH/LH-RH. A wedge biopsy provided ovarian tissue for histological and histochemical studies of steroid dehydrogenase activity. Treatment with FSH/LH-RH caused a trophic effect on the ovaries, with evidence of follicular development; ovulation occurred in two out of 16 treated women. Preovulatory mature follicles were found in three others.Clearly the FSH/LH-RH-induced release of FSH and LH caused follicular growth up to Graafian follicles, mature preovulatory follicles, and ovulation. Mitosis in granulosa and theca cells was also observed. A wide individual variation in gonadal response to hypothalamic FSH/LH-RH was evident, however. Nonetheless, our data support the possibility that treatment with FSH/LH-RH may prove valuable in patients with anovulatory sterility of hypothalamic origin.

Neuroendocrine mediating mechanisms: from the symbolic stimulus to the physiological response

Hypothalamic releasing factors are reviewed in the context of their importance to an understanding of neuroendocrine mediating mechanisms in psychobiology and psychosomatic medicine. Recent developments in research relating to corticotrophin, thyrotropin and gonadotropin releasing factors are the main focus of the discussion.

Luteinizing hormone and follicle stimulating hormone-releasing hormone test in patients with hypothalamic-pituitary-gonadal dysfunction

A standard intravenous 100 mug luteinizing hormone/follicle stimulating hormone-releasing hormone (LH/FSH-RH) test was used to assess the pituitary gonadotrophin responses in 155 patients with a variety of diseases of the hypothalamic-pituitary-gonadal axis. In all but nine patients there was an increase in circulating levels of either LH or FSH in response to the releasing hormone though 137 (88%) were clinically hypogonadal. It was not possible with this test to distinguish between hypothalamic and pituitary causes of hypogonadotrophic hypogonadism, since a variety of LH and FSH responses emerged within the disease groups. However, primary gonadal failure characteristically resulted in exaggerated gonadotrophin response. The potential therapeutic use of the gonadotrophin releasing decapeptide is suggested in certain patients with hypogonadotrophic hypogonadism.

Hypothalamic regulatory hormones

The molecular structures of several polypeptides isolated from hypothalamic tissue have been established and the synthesis of these compounds has been achieved. These polypeptides selectively stimulate or inhibit the release of anterior pituitary hormones and melanocyte-stimulating hormone. Various studies indicate their important physiological role and support the concept that some of these polypeptides are hormones. Some synthetic hypothalamic hormones and their derivatives may find important clinical and veterinary applications.

Stimulation of adenosine 3':5'-cyclic monophosphate accumulation in anterior pituitary gland in vitro by synthetic luteinizing hormone-releasing hormone

A near-maximal dose (20 ng/ml) of synthetic luteinizing hormone(LH)-releasing hormone/follicle-stimulating hormone(FSH)-releasing hormone added to incubated anterior pituitary tissue of male rats leads to concomitant increases of intracellular concentrations of adenosine 3':5'-monophosphate and of release of both LH and FSH. The stimulatory effect of LH-releasing hormone/FSH-releasing hormone is observed after a lag period of about 90 min and is progressive at later time intervals; a 3-fold stimulation of cAMP accumulation over control is seen after 210 min of incubation. Half-maximal stimulation of cAMP accumulation is observed between 0.1 and 1.0 ng/ml (0.1-1 nM) of LH-releasing hormone/FSH-releasing hormone. In the presence of 10 mM theophylline, the stimulatory effect of LH-releasing hormone/FSH-releasing hormone on cAMP accumulation is similar to that observed in the absence of the inhibitor of cyclic nucleotide phosphodiesterase, indicating that the releasing hormone exerts its effect by specific activation of adenylate cyclase in LH- and FSH-secreting cells rather than by inhibition of cyclic nucleotide phosphodiesterase. Since the release of growth hormone, thyrotropin, prolactin, and adrenocorticotropic hormone is not affected by LH-releasing hormone/FSH-releasing hormone, and since cAMP stimulates the release of all six adenohypophyseal hormones. the observed changes of cAMP concentrations indicate specific stimulation of adenylate cyclase activity in LH-and FSH-secreting cells of the adenohypophysis.

Hormonal responses to synthetic luteinizing hormone and follicle stimulating hormone-releasing hormone in man

The effects of the gonadotrophin-releasing hormone, synthetic decapeptide luteinizing hormone/follicle stimulating hormone-releasing hormone (LH/FSH-RH), have been studied in 18 normal men and five women in the follicular phase of their menstrual cycle. Rapid and dose-dependent (25 to 100 mug) increases in serum immunoreactive LH were seen, which reached a peak 20 to 30 minutes after a rapid intravenous injection. Similar but much smaller increases in serum immunoreactive FSH were seen. These conclusions have been validated by using two different immunoassay systems for each hormone. The LH/FSH-RH therefore causes both LH and FSH release in man as in animals but does not affect growth hormone, thyrotrophin, or ACTH. The gonadotrophin responses were the same in the women as in the men but were insufficient in the men to cause statistically significant changes in the serum levels of the gonadal steroid hormones, testosterone or oestradiol, or in their precursors 17 alpha-hydroxyprogesterone or progesterone. In the women, however, there was a rise in oestradiol after the 100-mug doses. The use of LH/FSH-RH will provide an important test to define the level of the lesion in hypogonadal patients and also should be valuable in the treatment of some types of male and female infertility. A simple and clinically useful LH/FSH-RH test of pituitary function is described (100 mug given intravenously), and the provisional normal responses of LH and FSH at 20 and 60 minutes are given.