Reduced 'gonadotrophin response to releasing hormone' after chronic administration to impotent men

Pros and cons of GnRHa treatment for early puberty in girls

The timing of puberty has considerable biological, psychosocial and long-term health implications. Secular trends in age at pubertal development, the effects of obesity and the potential effects of environmental endocrine disruptors challenge the standard definitions of precocious puberty and the indications for intervention with gonadotropin-releasing hormone agonists (GnRHa) in girls with precocious puberty. GnRHa therapy is effective in improving adult height in patients who present with classic central precocious puberty (at <8 years old), without causing adverse effects on body composition, BMD and reproductive function. However, its benefits in patients with atypical forms of early puberty not driven by luteinising hormone are not well defined. The role of GnRHa in these patients and the potential benefits in terms of later growth, psychosocial functioning and long-term risk of adult diseases that are associated with early menarche, such as breast cancer and the metabolic syndrome, have not been established.

Free alpha-subunit is superior to luteinizing hormone as a marker of gonadotropin-releasing hormone despite desensitization at fast pulse frequencies

A pulsatile pattern of GnRH stimulation is essential for normal secretion of luteinizing hormone (LH), while both continuous and fast-frequency GnRH stimulation result in a paradoxical decrease in gonadotrope responsiveness known as desensitization. Under physiological conditions there is striking concordance between the pulsatile secretion of LH and the glycoprotein free alpha-subunit (FAS). The aims of this study were to determine whether the FAS response to GnRH is also decreased at fast frequencies of GnRH stimulation and whether FAS is superior to LH as a marker of GnRH secretory activity at fast-pulse frequencies. The model of GnRH-deficient men was chosen to permit precise control of the dose and frequency of GnRH stimulation of the gonadotrope. The frequency of i.v. administration of GnRH to 5 GnRH-deficient men was progressively increased from every 120 to every 60 min, from 60 to 30 min, and from 30 to 15 min during three 12-h admissions, 1 week apart. The bolus dose of GnRH remained constant and was set at that dose previously shown to produce physiological concentrations and amplitudes of LH secretion and normal testosterone levels. As the frequency of GnRH stimulation was increased, a progressive rise in mean FAS levels was noted (353 +/- 13, 448 +/- 42, 466 +/- 50, and 698 +/- 85 ng/L [mean +/- SEM] for 120, 60, 30, and 15 min intervals; P < 0.005). However, normalization of mean FAS levels to account for the increase in total GnRH delivered with increasing frequencies revealed a progressive decrease in pituitary responsiveness to each GnRH bolus with increasing frequency of stimulation (353 +/- 13, 224 +/- 21, 117 +/- 13, 87 +/- 11 ng/L; P < 0.001). The decrease in normalized mean levels was supported by a decrease in the FAS pulse amplitude with increasing frequency (517 +/- 53, 365 +/- 50, 176 +/- 29 ng/L for 120, 60, and 30 min intervals, respectively; P < 0.005). At interpulse intervals of 120 and 60 min, there was complete concordance of LH and FAS pulses in response to GnRH. However, at the 30-min frequency FAS proved to be a better marker of GnRH with a higher true positive rate and lower number of false positives than LH (P < 0.05). At all frequencies, the number of false positive pulses detected tended to be lower for FAS than for LH (P = 0.06). From these data we conclude that FAS is subject to desensitization in response to increasing frequencies of GnRH administration in GnRH-deficient men, but is superior to LH as a surrogate marker of GnRH pulse generator activity at fast pulse frequencies.

Sexual behavior of men with isolated hypogonadotropic hypogonadism or prepubertal anterior panhypopituitarism

Sexual behavior of men with secondary hypogonadism was studied. Seven of the thirteen subjects presented with hypogonadism secondary to isolated gonadotropin (Gn) deficit, whereas the other six had idiopathic prepubertal anterior panhypopituitarism. Testosterone (T) levels were low and did not differ between the two groups. All subjects were evaluated both during replacement therapy (Gn in the first group; Gn plus cortisone and thyroxine in the second group) and 2 months after withdrawal of Gn therapy. During and after withdrawal of Gn administration, men with isolated deficit of Gn retained sexual activity and nocturnal penile tumescence, although they were partially compromised compared with a control group; on the other hand, panhypopituitarics reported compromised sexual function during Gn treatment and no sexual function when Gn therapy was not given. We conclude that different lesions of the hypothalamus-pituitary axis were accompanied by varying degrees of sexual impairment in the two groups of men presenting both secondary hypogonadism and very low T levels.

Is yohimbine effective in the treatment of organic impotence? Results of a controlled trial

Yohimbine is an alpha-adrenoceptor blocker that has been used in the treatment of erectile dysfunction. Adequate trials of this substance in a clearly defined organically impotent population are not available. We conducted a randomized, controlled study with partial cross-over of yohimbine versus placebo in 100 organically impotent men. The first phase of the study showed a positive response in 42.6 per cent of the patients receiving yohimbine versus 27.6 per cent in the placebo group. Although favorable to the test medication these values did not reach statistical significance (p equals 0.42). A similar pattern was noted in the second phase of the study. The over-all response rate of 43.5 per cent was consistent with a previous noncontrolled trial but it was much lower than previous studies. The response rate of organically impotent patients to yohimbine is at best marginal. Owing to its ease of administration, safety and modest effect it still is used in those patients who do not accept more invasive methods. Adrenoceptors are involved in the erectile process, although other neurotransmitter systems also are putative modulators of penile erection, including cholinergic, dopaminergic and vasoactive intestinal polypeptide pathways. It is beyond reasonable expectation that a single agent be of value for all cases of organic impotence. However, yohimbine has shown modest effectiveness at the doses used in this trial (18 mg. per day). Higher doses or a different route of administration may produce different effects.

Gonadotropin-releasing hormone differentially regulates expression of the genes for luteinizing hormone alpha and beta subunits in male rats

Gonadotropin-releasing hormone (GnRH) and gonadal steroids regulate synthesis and release of luteinizing hormone (LH). GnRH is secreted intermittently by the hypothalamus, producing pulsatile LH release, and a pulsatile GnRH stimulus is required to maintain LH secretion. We report the regulatory effects of GnRH pulse injections on pituitary concentrations of LH alpha and beta subunit mRNAs in a castrated/testosterone-replaced male rat model. Replacement with physiologic amounts of testosterone decreased concentrations of both LH subunit mRNAs. GnRH pulse injections (10-250 ng per pulse given every 30 min for 48 hr) increased both mRNA concentrations, but the dose response patterns were markedly different. alpha subunit mRNA was increased by all GnRH doses but not the levels seen after castration alone. In contrast, LH beta subunit mRNA concentrations showed a marked dependence on GnRH dose. Maximal responses, to values similar to those in castrates, occurred after 25-ng GnRH pulses, and larger doses produced a smaller increase in LH beta subunit mRNA. Both the acute LH secretory response to GnRH and the number of GnRH receptors followed a pattern similar to the LH beta subunit mRNA concentration and were maximal after the 25-ng GnRH dose. These results show that GnRH can differentially regulate LH subunit mRNAs and suggest that concentrations of LH beta subunit mRNA may be a limiting factor in GnRH-stimulated LH release.

Testosterone receptors in corpora cavernosa of penis

Despite existing information that most impotent patients have normal serum testosterone, testosterone is still used frequently in the treatment of impotence. In 11 patients who underwent penile implantation, we measured the presence of testosterone receptors in the corpora cavernosa. An average value of 1.82 fmol/mg of protein cytosol was found in this group of patients. This value is too low to obtain any significant improvement in erectile function following testosterone application. Testosterone hypogonadism will likely remain the only indication in which testosterone application might improve organically triggered impotence.

Testicular histology following chronic gonadotropin-releasing hormone agonist treatment

The histologic appearance of the testes of men exposed to chronic gonadotropin-releasing hormone agonist (GnRH-A) therapy has not been previously documented. Herein, we report on the histologic features of the testes of four patients with disseminated prostatic carcinoma who received at least 1 year of daily treatment with (D-Leu6, des-Gly-NH2(10), proethylamide9)-GnRH (leuprolide, Abbott Laboratories, North Chicago, IL) for their disease, and subsequently underwent bilateral orchiectomy. In marked contrast to the testes from five control patients, the testes of these agonist-treated patients demonstrated absence of spermatogenesis, Leydig cell hypoplasia, and Leydig cell inactivity. These data provide direct histologic evidence that the chronic administration of GnRH agonists may be suitable as a potential male contraceptive.

Regulation of pituitary gonadotropin-releasing hormone receptors by pulsatile gonadotropin-releasing hormone injections in male rats. Modulation by testosterone

The pattern of the gonadotropin-releasing hormone (GnRH) stimulus is critically important in the regulation of pituitary gonadotropin secretion and continuous infusions down-regulate secretion while intermittent pulses maintain luteinizing hormone (LH) and follicle-stimulating hormone (FSH) responsiveness. We examined the effects of pulsatile GnRH administration on pituitary GnRH receptors (GnRH-R) and gonadotropin secretion in the presence of physiological concentrations of testosterone (T) to elucidate the mechanisms and sites of action of GnRH and T on the pituitary gonadotroph. Castrate male rats received one, two, or four testosterone (T) implants (serum T concentrations of 1.1, 2.4, and 5.2 ng/ml, respectively) to suppress endogenous GnRH secretion. Subsequently, intracarotid pulse injections of GnRH (5-250 ng/pulse) or saline in controls were given every 30 min for 48 h, after which gonadotropin responses and pituitary GnRH-R were measured. In control rats, the T implants prevented the rise in GnRH-R that was seen in castrates (empty implant--600 fmol/mg protein) and maintained receptors at the level that was present in intact animals (300 fmol/mg). Pulsatile GnRH administration increased GnRH-R in castrate T-implanted rats, but the response was dependent on the serum T concentration. With one T implant, increasing GnRH doses per pulse stimulated GnRH-R in a linear manner and the maximum receptor concentration (703 +/- 99 fmol/mg) was seen after the 250 ng GnRH dose. In the presence of two T implants, GnRH-R was maximal (705 +/- 45 fmol/mg) after the 25-ng dose and higher doses did not increase receptors above control values. With four T implants, GnRH doses of 5 ng induced a maximum response, 17-50 ng/pulse did not increase GnRH-R, but receptors were again increased by the 250-ng dose (633 +/- 86 fmol/mg). After 48 h of pulsatile GnRH administration there was no correlation between the number of GnRH-R and LH responses to GnRH. In rats with one or two T implants, LH responses were absent after all but the 250-ng doses. In contrast, LH responsiveness was not impaired in the presence of four implants. Thus, low dose GnRH pulses down-regulate LH secretion by an action at a post GnRH-R site, and this effect is regulated by testosterone. The results show that GnRH, given in a pulsatile manner, regulates its own receptor, and physiological increases in serum T produce a 50-fold increase in the sensitivity of GnRH-R stimulation by GnRH.

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.

Familial idiopathic gonadotropin deficiency: a hypothalamic form of hypogonadism

To date, familial idiopathic gonadotropin deficiency (FIGD) has not been delineated as either a hypothalamic or a pituitary form of hypogonadism. Leydig cell sensitivity to human chorionic gonadotropin (HCG) has also been suggested as subnormal in FIGD. Also, in a few previously reported families the Kallmann syndrome was not clearly ruled out. Data herewith reported on three sibs with FIGD supported the following conclusions: 1) FIGD is due to insufficient hypothalamic luteinizing hormone-releasing hormone (LRH) secretion, 2) the sensitivity of Leydig cells to HCG is normal, 3) LRH treatment may be helpful in these patients, 4) an associated hypothalamic-pituitary-prolactin (PRL) dysfunction may also be present, and 5) FIGD and the Kallmann syndrome are different entities having a similar pathophysiology but different cause and overall clinical picture.

Effect of GnRH superactive analogs (alone and combined with androgen) on testicular function in man and experimental animals

GnRH long acting agonists, when given chronically, are potent inhibitors of testicular function in both man and experimental animals. Administration of these agents to male rats and to men results in suppression of testosterone secretion and diminished sperm counts. Despite the similarity of these observations the mechanisms by which these agents effect the testes appear to be different in the two species. In man GnRH analogs have an early stimulatory effect on LH and FSH secretion with down regulation evident by the 10th day of daily treatment. Longer treatment results in suppressed LH, FSH and testosterone levels. In the rat the stimulatory phase of GnRH analogs on LH and FSH secretion persisted for a much longer period of time (20-60 days). In the rat, direct testicular effects of analogue were the most likely cause of early suppression of testosterone and impaired sperm production. In both species combined testosterone and GnRH analog had additive effects on gonadotropin hormone suppression; combined therapy is being tested as a male contraceptive regimen.

Hypogonadotrophic hypogonadism resistant to hCG and responsive to LHRH: report of a case

The treatment of hypogonadotrophic hypogonadism with gonadotrophin releasing hormone (LHRH) has proved difficult in the past because of a progressive decline in the pituitary gonadotrophin response. These early studies generally used large relatively infrequent doses of natural LHRH (Davies et al., 1977) or analogues with a prolonged action (Smith et al., 1979). Recently, several reports have indicated that the lack of gonadotrophin response to LHRH can be overcome by frequent administration of low doses of natural LHRH in a pulsatile fashion (Belchetz et al., 1978; Crowley et al., 1980; Jacobson et al., 1979; Schoemaker et al., 1981; Valk et al., 1980). However, it is not known whether those patients with hypogonadotrophic hypogonadism who fail to respond to human chorionic gonadotrophin (hCG) (Bardin et al., 1969) are capable of responding to LHRH. In this case report of a patient with hypogonadotrophic hypogonadism who was resistant to prolonged hCG therapy, normal pituitary gonadotrophin and testosterone responses were obtained following pulsatile LHRH administration. The sperm count rose to 11 X 10(6)/ml. His wife became pregnant and was delivered of a normal healthy female infant after an uneventful pregnancy.

Treatment of hypogonadotropic hypogonadal male patients with the luteinizing hormone-relasing hormone (LH-RH) anolog D-Ser(TBU)6 EA10 LH-RH: transient disappearance of gonadotropin stimulation

We have studied the effect of prolonged treatment with a long-acting luteinizing hormone-releasing hormone (LH-RH) analog (D-Ser-(TBU)6 EA10 LH-RH in six patients with isolated gonadotropin deficiency. Before treatment, all subjects responded to LH-RH (100 microgram intravenously [IV]); one responded immediately, and five after 5 daily infusions of LH-RH (200 microgram). Treatment by LH-RH analog (348 microgram every 2 days with a nasal spray for 90 or 120 days) is only efficient for 1 month; a consistent increase in serum LH and a slight increase in testosterone (T) were observed in all patients, but no increase of serum follicle-stimulating hormone (FSH) was detectable. Then a paradoxical effect appeared: LH and T levels returned to the basal values. Moreover, this treatment induced refractoriness of the pituitary to LH-RH for several months after the end of treatment. The appearance of antibodies to LH-RH and LH-RH analog was eliminated. A pituitary response was obtained in three patients when a new LH-RH stimulation was repeated 7 and 11 months after the end of treatment. The mechanism of this pituitary desensitization is discussed.

Short-term treatment of idiopathic precocious puberty with a long-acting analogue of luteinizing hormone-releasing hormone. A preliminary report

The uncoupling of pituitary stimulation and response observed in adults during administration of the luteinizing hormone-releasing hormone analogue, D-Trp6-Pro9-NEt-LHRH (LHRHa) suggested that this drug might be useful in treating precocious puberty. We treated five girls with idiopathic precocious puberty (ages two to eight) for eight weeks with daily subcutaneous injections of LHRHa. The patients had Tanner II to IV pubertal development, advanced bone age, an estrogen effect on vaginal smear, measurable basal gonadotropin levels with pulsed nocturnal secretion, and a pubertal gonadotropin response to LHRH. Irregular vaginal bleeding was present in three patients. LHRHa significantly decreased basal (P less than 0.025) and LHRH-stimulated (P less than 0.01) gonadotropin levels as well as serum estradiol (P less than 0.05). The vaginal maturation-index score, which reflects the estrogen effect, fell by 25 per cent. Eight weeks after stopping treatment, all hormonal values and the vaginal maturation index had returned to pretreatment levels. These favorable short-term results will need further study before the benefits and risks of chronic treatment with LHRHa can be adequately assessed.

The effects of different dose regimes of D-SER(TBU)6-LHRH-EA10 (HOE 766) in subjects with hypogonadotrophic hypogonadism

Eight male patients with hypogonadotrophic hypogonadism were treated with injections of a long acting LHRH analogue, HOE 766. Six of the patients were on daily subcutaneous injections of 5 microgram of this analogue at the start of this study and were changed to alternate-daily injections of the same dose for 1-3 months. They were then treated with twice-daily injections of 0.5 microgram HOE 766, as was another subject not previously treated. The HOE 766 twice-daily was given alone for 1 or 2 months and then sex steroid replacement therapy was added to this for a further 4-5 months. There was no clinical improvement or rise in plasma testosterone levels until sex steroid therapy was commenced. Basal LH and FSH levels and peak responses to 100 microgram LHRH remained low throughout the study. It is concluded that these variations in dose and interval of administration do not overcome the lack of pituitary response which is a feature of prolonged treatment with LHRH analogues.

The effect of chronic administration of a synthetic LH-RH analogue intranasally in cryptorchid boys

Eighteen boys with either unilateral or bilateral cryptorchidism were treated with a synthetic LH-RH analogue ("D-Leu 6, Des-Gly-10 LH-RH ethylamide") intranasally. The peptide was dissolved in aqueous solution (25 micrograms in 0,2 ml) and administered in the form of nasal drops. The patients were divided in two groups: in group A, 50 micrograms of the synthetic LH-RH analogue were administered intranasally every 48 h for 36 days; in group B same dose was given every 24 h. Additionally, in 4 cases a LH-RH test prior the trial was performed with the same peptide. The nasal administration resulted in a fivefold increase of LH and of FSH plasma concentration in 30 min and in 60 min, respectively. The endocrine profiles for T, LH and FSH were studied in each group over the treatment period and in group B (same dose was given every 24 h) a significant decrease of the LH and FSH plasma levels could be found. The clinical effect of treatment was same in the both groups. In the whole material 44% had either unilateral or bilateral descent of the testis after the therapy.

Comparison of pituitary response to regular GnRH, analogue (D-TRP6) and placebo

Pituitary response to synthetic regular GnRH, to a potent analogue (D-TRp6) and to placebo were compared in ten azoospermic males. FSH and LH were measured prior to and at given intervals following administration of each substance. In addition, plasma levels of testosterone and prolactin were measured. There was no significant difference in the magnitude of FSH and LH release following injection of their the regular or the analogue form of GnRH. However, plasma gonadotrophins remained elevated for significantly longer time periods following the administration of the analogue GnRH. In those patients in whom LH levels remained elevated for at least 24 hours the observation of elevated testosterone levels permitted the inference of adequate biological activity of endogenously produced LH. Patients who did not respond to the regular GnRH were also non-responsive to D-TRp6 GnRH. A surprising finding ws elevated prolactin levels 4-6 hours following GnRH administration. Placebo had no influence on gonadotrophins, testosterone and prolactin.

Effect of intranasal LHRH therapy on plasma LH, FSH and testosterone, and relation to clinical results in prepubertal boys with cryptorchidism

Synthetic LHRH (HOE 471) administered intranasally over a period of 4 weeks for treatment of uni- or bilateral cryptorchidism in nineteen otherwise healthy prepubertal boys led to increased basal and peak LH values and to markedly decreased peak FSH values in the i.v. LHRH test. Basal testosterone remained unchanged. Sixteen cryptorchid boys treated with placebo served as a control group. The reduced FSH response to i.v. LHRH could be due to induction of a gonadal feedback mechanism rather than pituitary depletion of FSH, in view of the favourable therapeutic effect and the increased LH secretion seen in some of our patients. Pretreatment LHRH tests were available in twenty successfully and in twenty-eight unsuccessfully treated boys. LH values were similar in both groups, whereas FSH peak values were significantly higher in boys who responded successfully to subsequent therapy. Testicular descent occurred most readily in boys with a large pool of easily releasable FSH and without a significant rise in testosterone (in contrast to HCG treatment). We suggest that FSH induces changes that potentiate the local action of testosterone.

Activation of pituitary gonadotropic function by an agonist of luteinizing hormone-releasing factor in the puerperium

To test the hypothesis that long-term deprivation of endogenous luteinizing hormone-releasing factor (LRF) during the course of pregnancy may account for the lack of gonadotropin in the puerperium, six normal postpartum women were treated with the potent and long-acting LRF agonist (D-Trp6, Pro9-NEt)-LRF. A 50 microgram dose of LRF agonist was administered subcutaneously every 48 hours for four doses, with the first dose given on the first day post partum. Prior to treatment, each subject was tested with two pulses of LRF (10 micrograms at 2 hour intervals) and again at the end of LRF agonist treatment on day 10 post partum. Pulses of LRF induced no significant elevation of follicle-stimulating hormone (FSH) levels on day 1 post partum. During treatment, a significant (P less than 0.005) increase in basal FSH levels occurred after the second dose of LRF agonist administration. Following treatment, pulses of LRF elicited a remarkable gonadotropin release with a relatively greater percent rise for FSH than for human chorionic gonadotropin-luteinizing hormone. Our data indicate that the lack of gonadotropin activity during the first 3 weeks post partum is, at least in part, related to insufficiency of endogenous LRF secretion and that resumption of gonadotropin secretion can be functionally activated by treatment with the appropriate dose and intervals of an LRF agonist.

Induction of puberty: long-term treatment with high-dose LHRH

Gonadotropin releasing hormone 500 mcg was administered twice daily to four patients (two male, two female) with hypogonadotrophic hypogonadism due to LHRH deficiency, for a minimum of 1 year. Despite initially encouraging biochemical responses and physical changes in all four patients, gonadotrophin responsiveness waned, sex steroid levels were not maintained and pubertal development has not occurred. This diminishing responsiveness appears to be a severe limitation on the use of LHRH as a therapeutic agent.

Comparison of long-acting analogues of luteinizing hormone releasing hormone in man

Currently, LHRH, when used therapeutically, is given by parenteral injection every 8 h. We have looked at the release of LH and FSH induced by five analogues of LHRH and compared this with gonadotrophin release after synthetic LHRH. The analogues were substituted in position 6 or in positions 6 and 10 and were given intravenously, intranasally or subcutaneously in three separate studies. After intravenous administration of 100 micrograms, all analogues caused greater release of LH and FSH than did synthetic LHRH. Given intranasally in a dose of 500 micrograms, three of the four analogues tested caused greater LH and FSH release than did LHRH. With tryptophan substitution in position 6 (D-TRP6-LHRH), mean LH levels in five subjects were still above the normal range 24 h after a single intranasal dose. The intranasal administration of selected analogues of LHRH has great potential in the treatment of conditions associated with deficient gonadotrophin secretion, provided that pituitary overstimulation, which may eventually lead to a decrease in LH and FSH output by the anterior pituitary, is avoided.

The pituitary-gonadal response to the gonadotrophin releasing hormone analogue D-Ser (TBU)6-Des Gly10-LHRH-ethylamide in normal men

We have studied the dose-response characteristics of the LHRH analogue D-Ser (TBU)6-Des Gly10-LHRH-ethylamide administered subcutaneously to five normal male volunteers. The relative potency of the analogue is about sixty times (FSH) and forty times (LH) that of the parent peptide and the increased potency and duration of action of the analogue lead to enhanced biological effect in terms of testosterone release. The prolonged duration of action of the analogue suggests that a single daily dosage regime could be used although further chronic studies with this potent analogue should be undertaken in normal volunteers to determine optimum dosage schedules.

Treatment of cryptorchidism with a potent analog of gonadotropin-releasing hormone

Pernasal therapy of cryptorchidism with D-Leu6-des-Gly10-gonadotropin-releasing hormone ethylamide (D-Leu6-des-Gly10-GnRH-EA), a potent, long-acting GnRH analog, was attempted. Eleven prepubertal cryptorchid boys received between 25 microgram once daily and 25 to 50 microgram twice daily for 5 to 12 weeks. Complete testicular descent was achieved in 4 of the 11 boys. GnRH tests (1.5 microgram/kg intravenously), conducted in six boys before treatment, after 4 weeks of treatment, and in 2 boys 3 months after treatment, did not reveal changes in gonadotropin secretion indicative of precocious puberty or of decreased hypophyseal sensitivity to GnRH. Antibodies to the GnRH analog or to GnRH could not be detected.