Pulsatile Gonadotropin-releasing Hormone Administration Research Articles

Novel insights into minipuberty and GnRH: Implications on neurodevelopment, cognition, and COVID-19 therapeutics.

In humans, the first 1000 days of life are pivotal for brain and organism development. Shortly after birth, gonadotropin-releasing hormone (GnRH) neurons in the hypothalamus are activated, a phenomenon known as minipuberty. This phenomenon, observed in all mammals studied, influences the postnatal development of the hypothalamic-pituitary-gonadal (HPG) axis and reproductive function. This review will put into perspective the results of recent studies showing that the impact of minipuberty extends beyond reproductive function, influencing sensory and cognitive maturation. Studies in mice have revealed the role of nitric oxide (NO) in regulating minipuberty amplitude, with NO deficiency linked to cognitive and olfactory deficits. Additionally, findings indicate that cognitive and sensory defects in adulthood in a mouse model of Down syndrome are associated with an age-dependent decline of GnRH production, whose origin can be traced back to minipuberty, and point to the potential therapeutic role of pulsatile GnRH administration in cognitive disorders. Furthermore, this review delves into the repercussions of COVID-19 on GnRH production, emphasizing potential consequences for neurodevelopment and cognitive function in infected individuals. Notably, GnRH neurons appear susceptible to SARS-CoV-2 infection, raising concerns about potential long-term effects on brain development and function. In conclusion, the intricate interplay between GnRH neurons, GnRH release, and the activity of various extrahypothalamic brain circuits reveals an unexpected role for these neuroendocrine neurons in the development and maintenance of sensory and cognitive functions, supplementing their established function in reproduction. Therapeutic interventions targeting the HPG axis, such as inhaled NO therapy in infancy and pulsatile GnRH administration in adults, emerge as promising approaches for addressing neurodevelopmental cognitive disorders and pathological aging.

Pulsatile gonadotropin-releasing hormone: clinical applications of a physiologic paradigm

Gonadotropin-releasing hormone (GnRH) is a fundamental driver of human reproduction. A pulsatile pattern of GnRH secretion is essential to achieve pituitary stimulation, gonadotropin secretion, and normal gonadal function. Pulsatile GnRH administration is used to treat anovulation and male hypogonadotropic hypogonadism. Pulsatile GnRH ovulation induction is effective and safe because it allows to avoid ovarian hyperstimulation syndrome and reduce the occurrence of multiple pregnancies. This physiology-inspired therapeutic tool has also permitted to elucidate several pathophysiologic features of human reproductive disorders.

Use of pulsatile gonadotropin-releasing hormone (GnRH) in patients with functional hypothalamic amenorrhea (FHA) results in monofollicular ovulation and high cumulative live birth rates: a 25-year cohort

PurposeTo analyze outcomes of pulsatile administration of gonadotropin-releasing hormone (GnRH) in infertile women diagnosed with functional hypothalamic amenorrhea (FHA).MethodsA single-center retrospective cohort study was conducted from 1996 to 2020. Sixty-six patients with the diagnosis FHA that underwent therapy using the pulsatile GnRH pump for conception were included and analyzed. The primary outcome was the live birth rate (LBR). Secondary outcomes were the number of dominant follicles, ovulation rate, biochemical pregnancy rate (BPR), clinical pregnancy rate (CPR), miscarriage rate, and multiple pregnancy rate. A matched control group was selected to compare the birth weight of newborn children.ResultsDuring the study period, 66 patients with FHA underwent 82 treatments (14 of 66 patients had more than one treatment) and a total of 212 cycles (ovulation induction attempts) using pulsatile GnRH. The LBR per treatment was 65.9%. The ovulation rate per cycle was 96%, and monofollicular ovulation was observed in 75% of cycles. The BPR per treatment was 80.5%, and the cumulative CPR per treatment was 74.4%. The miscarriage rate was 11.5%. One dizygotic twin pregnancy was observed (1.6%). Average newborn birth weight (NBW) from patients with FHA was comparable to the control group.Conclusion(s)In patients with FHA, excellent pregnancy rates were achieved using the subcutaneous GnRH pump. The high cumulative LBR with normal NBW as well as low rates of multiple gestation indicate that the pulsatile GnRH pump represents a safer and more physiologic alternative to ovulation induction with injectable gonadotropins.Trial registrationEthics Committee Northwest and Central Switzerland (Ethikkommission Nordwest- und Zentralschweiz - EKNZ) - Project-ID 2020-01612.

The efficacy of pulsatile gonadotropin-releasing hormone therapy in male patients with hypogonadism caused by hypopituitarism

To evaluate the efficacy of pulsatile gonadotropin-releasing hormone (GnRH) therapy in patients with hypogonadism caused by hypopituitarism so as to guide clinical treatment. Clinical manifestations, laboratory examinations, and imaging features were collected from 22 patients with hypopituitarism that led to hypogonadism who were treated with pulsatile GnRH. Data were analyzed and the patients were followed up. The average age at which patients began to use pulsatile GnRH was 22.8±3.7 years old. The duration of pulsatile GnRH administration ranged from 3 to 60 months, with an average of 20.5±12.1 months. The dosage of GnRH administered was 10-12 µg/90 minutes. Patients were followed up for 26-81 months, with an average of 50.5±17.3 months. After pulsatile GnRH treatment, the clinical manifestations and hormone levels of these patients improved to varying degrees. The luteinizing hormone (LH) and testosterone (T) levels of 7 patients increased to the normal range, sperm could be detected in seminal fluid samples of 5 patients, and 2 patients successfully reproduced. Within the good-response group, 71.4% of patients achieved spermatogenesis within an average of 13 months of treatment. In patients who had poor response to gonadotropin therapy prior to pulsatile GnRH therapy, 25% achieved spermatogenesis, and 37.5% reached the normal range of LH and T. The levels of LH after pulsatile GnRH treatment was positively correlated with the peak levels of LH and testicular volume prior to treatment (P<0.01). Pulsatile GnRH therapy can improve gonadal function in most patients with hypogonadism caused by hypopituitarism. Patients were able to achieve spermatogenesis, especially in patients who were poor-responders to gonadotropin treatment. Patients with greater basal testicular volume may respond better to pulsatile GnRH treatment. The GnRH stimulation test not only helps to evaluate the reserve function of pituitary GnRH cells at a certain time but may also serve as a prognostic factor. The results of this study form a basis for guiding clinical therapeutic choices.

Insight Into the Ontogeny of GnRH Neurons From Patients Born Without a Nose.

The reproductive axis is controlled by a network of gonadotropin-releasing hormone (GnRH) neurons born in the primitive nose that migrate to the hypothalamus alongside axons of the olfactory system. The observation that congenital anosmia (inability to smell) is often associated with GnRH deficiency in humans led to the prevailing view that GnRH neurons depend on olfactory structures to reach the brain, but this hypothesis has not been confirmed. The objective of this work is to determine the potential for normal reproductive function in the setting of completely absent internal and external olfactory structures. We conducted comprehensive phenotyping studies in 11 patients with congenital arhinia. These studies were augmented by review of medical records and study questionnaires in another 40 international patients. All male patients demonstrated clinical and/or biochemical signs of GnRH deficiency, and the 5 men studied in person had no luteinizing hormone (LH) pulses, suggesting absent GnRH activity. The 6 women studied in person also had apulsatile LH profiles, yet 3 had spontaneous breast development and 2 women (studied from afar) had normal breast development and menstrual cycles, suggesting a fully intact reproductive axis. Administration of pulsatile GnRH to 2 GnRH-deficient patients revealed normal pituitary responsiveness but gonadal failure in the male patient. Patients with arhinia teach us that the GnRH neuron, a key gatekeeper of the reproductive axis, is associated with but may not depend on olfactory structures for normal migration and function, and more broadly, illustrate the power of extreme human phenotypes in answering fundamental questions about human embryology.

Two Families with Normosmic Congenital Hypogonadotropic Hypogonadism and Biallelic Mutations in KISS1R (KISS1 Receptor): Clinical Evaluation and Molecular Characterization of a Novel Mutation

Context KISS1R mutations have been reported in few patients with normosmic congenital hypogonadotropic hypogonadism (nCHH) (OMIM #146110).ObjectiveTo describe in detail nCHH patients with biallelic KISS1R mutations belonging to 2 unrelated families, and to functionally characterize a novel KISS1R mutation.ResultsAn original mutant, p.Tyr313His, was found in the homozygous state in 3 affected kindred (2 females and 1 male) from a consanguineous Portuguese family. This mutation, located in the seventh transmembrane domain, affects a highly conserved amino acid, perturbs the conformation of the transmembrane segment, and impairs MAP kinase signaling and intracellular calcium release. In the second family, a French Caucasian male patient with nCHH was found to carry two recurrent mutations in the compound heterozygous state (p.Leu102Pro/Stop399Arg). In this man, pulsatile GnRH (Gonadotropin Releasing Hormone) administration restored pulsatile LH (Luteinizing Hormone) secretion and testicular hormone secretion. Later, long-term combined gonadotropin therapy induced spermatogenesis, enabling 3 successive pregnancies that resulted in 2 miscarriages and the birth of a healthy boy.ConclusionWe show that a novel loss-of-function mutation (p.Tyr313His) in the KISS1R gene can cause familial nCHH, revealing the crucial role of this amino acid in KISS1R function. The observed restoration of gonadotropin secretion by exogenous GnRH administration further supports, in humans, the hypothalamic origin of the gonadotropin deficiency in this genetic form of nCHH.

Use of Cognitive Behavior Therapy for Functional Hypothalamic Amenorrhea

Behaviors that chronically activate the hypothalamic-pituitary-adrenal (HPA) axis and/or suppress the hypothalamic-pituitary-thyroidal (HPT) axis disrupt the hypothalamic-pituitary-gonadal axis in women and men. Individuals with functional hypothalamic hypogonadism typically engage in a combination of behaviors that concomitantly heighten psychogenic stress and increase energy demand. Although it is not widely recognized clinically, functional forms of hypothalamic hypogonadism are more than an isolated disruption of gonadotropin-releasing hormone (GnRH) drive and reproductive compromise. Indeed, women with functional hypothalamic amenorrhea display a constellation of neuroendocrine aberrations that reflect allostatic adjustments to chronic stress. Given these considerations, we have suggested that complete neuroendocrine recovery would involve more than reproductive recovery. Hormone replacement strategies have limited benefit because they do not ameliorate allostatic endocrine adjustments, particularly the activation of the adrenal and the suppression of the thyroidal axes. Indeed, the rationale for the use of sex steroid replacement is based on the erroneous assumption that functional forms of hypothalamic hypogonadism represent only or primarily an alteration in the hypothalamic-pituitary-gonadal axis. Potential health consequences of functional hypothalamic amenorrhea, often termed stress-induced anovulation, may include an increased risk of cardiovascular disease, osteoporosis, depression, other psychiatric conditions, and dementia. Although fertility can be restored with exogenous administration of gonadotropins or pulsatile GnRH, fertility management alone will not permit recovery of the adrenal and thyroidal axes. Initiating pregnancy with exogenous means without reversing the hormonal milieu induced by chronic stress may increase the likelihood of poor obstetrical, fetal, or neonatal outcomes. In contrast, behavioral and psychological interventions that address problematic behaviors and attitudes, such as cognitive behavior therapy (CBT), have the potential to permit resumption of full ovarian function along with recovery of the adrenal, thyroidal, and other neuroendocrine aberrations. Full endocrine recovery potentially offers better individual, maternal, and child health.

Subcutaneous administration of pulsatile gonadotropin-releasing hormone decreases serum follicle-stimulating hormone and luteinizing hormone levels in women with polycystic ovary syndrome: A preliminary study

The main objectives of this study were to investigate whether [1] subcutaneous (SC) administration of pulsatile gonadotropin-releasing hormone (GnRH) decreases the increased levels of luteinizing hormone (LH) observed in women with polycystic ovary syndrome (PCOS); and [2] GnRH administration modifies the pattern of LH secretion observed in these patients. Serum follicle-stimulating hormone (FSH) and LH levels and LH pulse amplitude and pulse interval were determined in 13 patients with PCOS during the first 3 days of the cycle following the administration of 10 mg of medroxyprogesterone acetate during 5 days. Infertility clinic. Thirteen women with PCOS. Determination of FSH and LH serum levels after SC administration of pulsatile GnRH. The FSH and LH levels in serum. Mean FSH and LH levels in serum decreased following the administration of subcutaneous pulsatile GnRH in all treated women compared with baseline values. The LH pulse amplitude and pulse interval decreased in all patients following the administration of pulsatile GnRH. The SC administration of pulsatile GnRH in women with PCOS significantly decreases FSH and LH levels in serum. A decrease in the secretion of gonadotropins, without reaching the intense suppression observed with GnRH analogues, could be of great utility in in vitro fertilization (IVF) treatments.

Pulsatile gonadotrophin releasing hormone for ovulation induction in subfertility associated with polycystic ovary syndrome.

In normal menstrual cycles, gonadotrophin releasing hormone (GnRH) secretion is pulsatile, with intervals of 60-120 minutes in the follicular phase. Treatment with pulsatile GnRH infusion by the intravenous or subcutaneous route using a portable pump has been used successfully in patients with hypogonadotrophic hypogonadism. Assuming that the results would be similar in women with polycystic ovary syndrome (PCOS), pulsatile GnRH has been used to induce ovulation in these women. Although ovulation and pregnancy have been achieved, the effectiveness of pulsatile GnRH in women with PCOS has not been clearly demonstrated. To assess the effectiveness of pulsatile GnRH administration in women with polycystic ovary syndrome (PCOS), in terms of ongoing pregnancy, ovulation, clinical pregnancy, ovarian hyperstimulation syndrome (OHSS), multiple pregnancy, miscarriage, and multifollicular growth. We searched the Cochrane Menstrual Disorders & Subfertility Group trials register (searched 13 August 2003), the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library Issue 2, August 2001), MEDLINE (January 1966 to August 2003), EMBASE (January 1985 to August 2003) and reference lists of articles. We also contacted manufacturers and researchers in the field. All relevant published randomised clinical trials were selected for inclusion if treatment consisted of pulsatile GnRH administration versus another treatment for ovulation induction in subfertile women with PCOS. Relevant data were extracted independently by two reviewers (NB, MW). Validity was assessed in terms of method of randomisation, completeness of follow-up, presence or absence of crossover and co-intervention. All trials were screened and analysed for predetermined quality criteria. 2X2 tables were generated for all the relevant outcomes. Odds ratios were generated using the Peto method. Four randomised clinical trials involving 57 women were identified comparing four different treatments: GnRH versus HMG, GnRH and FSH versus FSH, GnRH following pretreatment with GnRH agonist (GnRHa) versus GnRH only, GnRH following pretreatment with GnRHa versus clomiphene citrate. This means that there was only one trial in any one comparison. In two studies, data of pre- and post-crossover were not described separately. All trials were small and of too short duration to show any significant differences in pregnancy results. The odds ratio for ongoing pregnancy, only described in one trial, was 7.5 (95% CI 0.44 to 127) in the comparison GnRH following pretreatment with GnRHa versus GnRH only in favour of the first group. Multiple pregnancies were not seen. Ovarian hyperstimulation syndrome was seen only in women allocated to ovulation induction with HMG. The four trials describing four different comparisons with a short follow up (1 to 3 cycles) were too small to either prove or discard the value of pulsatile GnRH treatment in patients with polycystic ovary syndrome.

Five-Day Pulsatile Gonadotropin-Releasing Hormone Administration Unveils Combined Hypothalamic-Pituitary-Gonadal Defects Underlying Profound Hypoandrogenism in Men with Prolonged Critical Illness

Five-Day Pulsatile Gonadotropin-Releasing Hormone Administration Unveils Combined Hypothalamic-Pituitary-Gonadal Defects Underlying Profound Hypoandrogenism in Men with Prolonged Critical Illness

Five-Day Pulsatile Gonadotropin-Releasing Hormone Administration Unveils Combined Hypothalamic-Pituitary-Gonadal Defects Underlying Profound Hypoandrogenism in Men with Prolonged Critical Illness1

Central hyposomatotropism and hypothyroidism have been inferred in long-stay intensive care patients. Pronounced hypoandrogenism presumably also contributes to the catabolic state of critical illness. Accordingly, the present study appraises the mechanism(s) of failure of the gonadotropic axis in prolonged critically ill men by assessing the effects of pulsatile GnRH treatment in this unique clinical context. To this end, 15 critically ill men (mean +/- SD age, 67 +/- 12 yr; intensive care unit stay, 25 +/- 9 days) participated, with baseline values compared with those of 50 age- and BMI-matched healthy men. Subjects were randomly allocated to 5 days of placebo or pulsatile iv GnRH administration (0.1 microg/kg every 90 min). LH, GH, and TSH secretion was quantified by deconvolution analysis of serum hormone concentration-time series obtained by sampling every 20 min from 2100-0600 h at baseline and on nights 1 and 5 of treatment. Serum concentrations of gonadal and adrenal steroids, T(4), T(3), insulin-like growth factor I (IGF), and IGF-binding proteins as well as circulating levels of cytokines and selected metabolic markers were measured. During prolonged critical illness, pulsatile LH secretion and mean LH concentrations (1.8 +/- 2.2 vs. 6.0 +/- 2.2 IU/L) were low in the face of extremely low circulating total testosterone (0.27 +/- 0.18 vs. 12.7 +/- 4.07 nmol/L; P < 0.0001) and relatively low estradiol (E(2); 58.3 +/- 51.9 vs. 85.7 +/- 18.6 pmol/L; P = 0.009) and sex hormone-binding globulin (39.1 +/- 11.7 vs. 48.6 +/- 27.8 nmol/L; P = 0.01). The molar ratio of E(2)/T was elevated 37-fold in ill men (P < 0.0001) and correlated negatively with the mean serum LH concentrations (r = -0.82; P = 0.0002). Pulsatile GH and TSH secretion were suppressed (P < or = 0.0004), as were mean serum IGF-I, IGF-binding protein-3, and acid-labile subunit concentrations; thyroid hormone levels; and dehydroepiandrosterone sulfate. Morning cortisol was within the normal range. Serum interleukin-1beta concentrations were normal, whereas interleukin-6 and tumor necrosis factor-alpha were elevated. Serum tumor necrosis factor-alpha was positively correlated with the molar E(2)/testosterone ratio and with type 1 procollagen; the latter was elevated, whereas osteocalcin was decreased. Ureagenesis and breakdown of bone were increased. C-Reactive protein and white blood cell counts were elevated; serum lactate levels were normal. Intermittent iv GnRH administration increased pulsatile LH secretion compared with placebo by an increment of +8.1 +/- 8.1 IU/L at 24 h (P = 0.001). This increase was only partially maintained after 5 days of treatment. GnRH pulses transiently increased serum testosterone by +174% on day 2 (P = 0.05), whereas all other endocrine parameters remained unaltered. GnRH tended to increase type 1 procollagen (P = 0.06), but did not change serum osteocalcin levels or bone breakdown. Ureagenesis was suppressed (P < 0.0001), and white blood cell count (P = 0.0001), C-reactive protein (P = 0.03), and lactate level (P = 0.01) were increased by GnRH compared with placebo infusions. In conclusion, hypogonadotropic hypogonadism in prolonged critically ill men is only partially overcome with exogenous iv GnRH pulses, pointing to combined hypothalamic-pituitary-gonadal origins of the profound hypoandrogenism evident in this context. In view of concomitant central hyposomatotropism and hypothyroidism, evaluating the effectiveness of pulsatile GnRH intervention together with GH and TSH secretagogues will be important.

Episodic leptin release is independent of luteinizing hormone secretion.

Several studies suggest that leptin modulates hypothalamic-pituitary-gonadal axis functions. Leptin may stimulate release of gonadotrophin releasing hormone (GnRH) from the hypothalamus and of gonadotrophins from the pituitary. A synchronicity of luteinizing hormone (LH) and leptin pulses has been described in healthy women and in patients with polycystic ovarian syndrome, suggesting that leptin may modulate the episodic secretion of LH. However, it has not been established whether LH regulates the episodic secretion of leptin. To further examine LH-leptin interactions, we studied the episodic fluctuations of circulating LH and leptin in two patients with Kallmann's syndrome (KS) before and on day 7 of pulsatile GnRH administration, and compared these with those observed in the early follicular phase of 10 regularly menstruating women divided into two control groups according to the body mass index of each patient. To assess episodic hormone secretion, blood samples were collected at 10 min intervals for 6 h, before and on day 7 of GnRH administration in KS patients, and during days 3-7 of the follicular phase in normally cycling women. LH and leptin concentrations were measured in all samples. For pulse analysis, the cluster algorithm was used. Before treatment, an apulsatile pattern with no endogenous LH pulsations was observed in both KS patients. However, leptin pulses were assessed in both women. During GnRH administration, pulsatile LH activity was achieved in both patients with pulse characteristics similar to those of the respective control group. Serum leptin concentrations and leptin pulsatile patterns were not modified. These results suggest that circulating leptin is probably not modulated by pulsatile GnRH-LH secretion.

Pulsatile luteinising hormone releasing hormone for ovulation induction in subfertility associated with polycystic ovary syndrome.

In normal menstrual cycles, gonadotrophin releasing hormone (GnRH) secretion is pulsatile, with intervals of 60-120 minutes in the follicular phase. Treatment with pulsatile GnRH infusion by the intra-venous or subcutaneous route using a portable pump has been used successfully in patients with hypogonadotrophic hypogonadism. Assuming that the results would be similar in polycystic ovary syndrome (PCOS), pulsatile GnRH has been used to induce ovulation in patients with PCOS. But, although ovulation and pregnancy has been achieved, the use of pulsatile GnRH in PCOS patients is controversial. To assess the effectiveness of pulsatile GnRH administration in women with clomiphene-resistant polycystic ovary syndrome (PCOS), in terms of ovulation induction, pregnancy, miscarriage, multiple pregnancy and ovarian hyperstimulation syndrome (OHSS). The search strategy of the Menstrual Disorders and Subfertility review group was used to identify all relevant trials. Please see Review Group details. All relevant published RCTs were selected. Non-randomised controlled trials were eligible for inclusion if treatment consisted of GnRH administration versus another treatment to induce ovulation in subfertile women with PCOS. A computerised MEDLINE and EMBASE search was used to identify randomised and non randomised controlled trials. The reference lists of all studies found were checked for relevant articles. One RCT (Bringer 1985a) and one abstract (Coelingh 1983) were identified this way. Relevant data were extracted independently by two reviewers (NB, MW). Validity was assessed in terms of method of randomization, completeness of follow-up, presence or absence of cross-over and co-intervention. All trials were screened and analysed for predetermined quality criteria. 2X2 tables were generated for all the relevant outcomes. Odds ratios were generated using the Peto modified Mantel-Haenszel technique. Three RCTs and one non-randomised comparative trial were identified comparing four different treatments: GnRH versus HMG, GnRH following GnRHa pre-treatment versus no pre-treatment, GnRH and FSH versus FSH, and GnRH following GnRHa pre-treatment versus GnRH following oral contraceptive pre-treatment. This means that there was only one trial in any one comparison. In the first two studies, data of pre- and post-cross-over were not described separately. Therefore, these results could not be included in the MetaView analysis. The odds ratio for ovulation rate was 16 (95 % CI: 1.1-239) in the study comparing GnRH and FSH with FSH. When GnRH after GnRHa pre-treatment was compared with GnRH after oral contraceptive pre-treatment, an odds ratio of 7.5 (95 % CI: 1.2-46) was obtained. All trials were small and of too short duration to show any significance in pregnancy results. Per study only one to four pregnancies occurred. Multiple pregnancies were not seen. OHSS was seen only in the patients stimulated with HMG. The four trials describing four different comparisons with a short follow up (1 to 3 cycles) were too small to either prove or discard the value of pulsatile GnRH treatment in patients with polycystic ovary syndrome.

Depression of FSH and LH secretion following pulsatile GnRH administration in ovariectomized women.

To investigate the mechanism by which pulsatile administration of gonadotrophin-releasing hormone (GnRH) modifies secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), we studied three groups of five women who had been ovariectomized for non-malignant gynaecological conditions at least 6 months previously, none of whom had received substitutional hormone therapy. Before and after 15 day treatment with subcutaneous pulsatile GnRH (one 20 microg dose every 90 min in group A, one 10 microg dose every 90 min in group B and one 20 microg dose every 120 min in group C), pulsatile secretion of LH and FSH was characterized by determining these hormones in 4 ml blood samples taken every 10 min for 8 h (9.00 a.m. to 5.00 p.m.). For both LH and FSH, mean serum concentration and pulse amplitude were lower after GnRH treatment than before (and in the case of LH the decrease depended upon both the size and frequency of exogenous GnRH pulses) but in no group was there a significant change in LH or FSH pulse frequency. We conclude that exogenous pulsatile GnRH probably acts by partially desensitizing the pituitary rather than by depressing endogenous GnRH secretion. Such partial desensitization would explain reports that exogenous pulsatile GnRH improves ovulation by women with polycystic ovary syndrome.

Gonadal and pituitary responsiveness of stallions is not down-regulated by prolonged pulsatile administration of GnRH.

The objective of this study was to determine if prolonged pulsatile administration of homologous gonadotropin-releasing hormone (GnRH) at therapeutic or 5x therapeutic doses would cause down-regulation of the stallion's hypothalamic-pituitary-testicular axis. Fifteen stallions were randomly assigned to three treatment groups (n=5/group) and received a 0.5 ml subcutaneous dose of saline (group 1), 50 microg GnRH (group 2), or 250 microg GnRH (group 3) every 2 hours for 75 days. Weekly evaluations of follicle stimulating hormone, luteinizing hormone, and testosterone and monthly evaluations of daily sperm output and spermatozoal motility failed to demonstrate any decreased pituitary or gonadal responsiveness within or among treatment groups (P > 0.1) as a result of treatment with GnRH. Results of this study demonstrate that the hypothalamic-pituitary-testicularaxis of the stallion, unlike that of other domestic species, is remarkably refractory to GnRH-induced down-regulation.

The effect of pulsatile gonadotropin-releasing hormone and estradiol administration on luteinizing hormone and follicle-stimulating hormone concentrations in pituitary stalk-sectioned ovariectomized pony mares

Hourly pulses of gonadotropin-releasing hormone (GnRH) or bi-daily injections of estradiol (E2) can increase luteinizing hormone (LH) secretion in ovariectomized, anestrous pony mares. However, the site (pituitary versus hypothalamus) of positive feedback of estradiol on gonadotropin secretion has not been described in mares. Thus, one of our objectives involved investigating the feedback of estradiol on the pituitary. The second objective consisted of determining if hourly pulses of GnRH could re-establish physiological LH and FSH concentrations after pituitary stalk-section (PSS), and the third objective was to describe the declining time trends of LH and FSH secretion after PSS. During summer months, ovariectomized pony mares were divided into three groups: Group 1 (control, n = 2), Group 2 (pulsatile GnRH (25 μg/hr), n = 3), and Group 3 (estradiol (5 mg/12 hr), n = 3). All mares were stalk-sectioned and treatment begun immediately after stalk-section. Blood samples were collected every 30 min for 8 h on the day before surgery (DO) and 5 d post surgery (D5) to facilitate the comparison of gonadotropin levels before and after pituitary stalk-section. Additionally, jugular blood samples were collected every 12 hr beginning the evening of surgery, allowing for evaluation of the gonadotropin secretory time trends over the 10 d of treatment. On Day 10, animals were euthanized to confirm pituitary stalk-section and to submit tissue for messenger RNA analysis (parallel study). Plasma samples were assayed for LH and FSH by RIA. Mean LH secretion decreased from Day 0 to Day 5 in Groups 1 and 3, whereas LH secretion tended (P < 0.08) to decrease in Group 2 mares. On Day 5, LH was higher (P < 0.01) in Group 2 (17.26 ± 3.68 ng/ml; LSMEANS ± SEM), than either Group 1 (2.65 ± 4.64 ng/ml) or group 3 (4.28 ± 3.68 ng/ml). Group 1 did not differ from Group 3 on Day 5 (P < 0.40). Similarly, mean FSH levels decreased in all groups after surgery, yet Group 2 mares had significantly (P < 0.001) higher FSH concentrations (17.66 ± 1.53 ng/ml) than Group 1 or Group 3 (8.34 ± 1.84 and 7.69 ± 1. 63 ng/ml, respectively). Regression analysis of bi-daily LH and FSH levels indicated that the time trends were not parallel. These findings indicate: 1) Pituitary stalk-section lowered LH and FSH to undetectable levels within 5 d after surgery, 2) pulsatile administration of GnRH (25 μg/hr) maintained LH and FSH secretion, although concentrations tended to be lower than on Day 0, and 3) E2 did not stimulate LH or FSH secretion.

Pituitary and gonadal responses to the long-term pulsatile administration of gonadotrophin-releasing hormone in fetal sheep.

The fetal hypothalamo-pituitary-gonadal axis reaches a peak in activity at mid-gestation and this is followed by a period of suppression which persists until the onset of puberty. The decline in gonadotrophic activity during late gestation is thought to reflect the maturation of central and peripheral feedback signals. In order to establish if sustained pituitary responsiveness is rate limiting to the reinstatement of reproductive function, we have examined the endocrine consequences of repeated pulsatile GnRH administration to male and fetal sheep during late gestation. Beginning on day 121 of gestation (term = 145 days) chronically catheterized fetal sheep were given i.v. pulses of either 500 ng GnRH or saline every 2 h for 14 days. Pituitary and gonadal responses were assessed by measuring changes in plasma concentrations of LH, FSH, inhibin and testosterone (in male fetuses) in response to the first pulse of GnRH on day 1 and to the corresponding pulse on days 4, 7, 10 and 14. In response to the first pulse of GnRH there was an immediate release of LH, with the peak response being significantly (P < 0.01) greater than on subsequent days. In male fetuses each pulse of LH was followed by a rise in plasma testosterone concentrations within 40-60 min. The amplitude of these testosterone responses increased significantly (P < 0.01) after 9 days of treatment despite a decline in the plasma LH response. Basal FSH concentrations increased progressively (P < 0.05) during pituitary stimulation with GnRH in both male and female fetuses. Immunoreactive inhibin concentrations were significantly (P < 0.05) higher in males than in females, and there was a gradual increase throughout the experimental period irrespective of treatment. We observed no inverse correlation between inhibin and FSH concentrations. These data show that pulsatile administration of GnRH to fetal sheep during late gestation results in sustained re-activation of pituitary-gonadal function. The decline in fetal gonadotrophins, which is a characteristic feature of late gestation, is therefore likely to result from inadequate GnRH secretion from the fetal hypothalamus rather than an inhibition of pituitary function by peripheral feedback signals.

Adult-onset idiopathic hypogonadotropic hypogonadism — A treatable form of male infertility: Nachtigall L.B.; Boepple P.A.; Pralong F.P.; Crowley W.F. Jr. USA New Engl J Med 1997 336/6 (410–415)

Background Men with isolated gonadotropinreleasing hormone (GnRH) deficiency typically present with an absence of pubertal development. We describe an adult-onset form of idiopathic hypogonadotropic hypogonadism that develops after puberty. Methods We studied 10 men (age, 27 to 57 years) with normal sexual maturation, idiopathic infertility, sexual dysfunction, low serum testosterone concentrations, and apulsatile secretion of luteinizing hormone on frequent blood sampling. All the men had otherwise normal anterior pituitary hormone secretion and sellar anatomy. We compared the results of semen analyses and measurements of testicular volume, serum testosterone, inhibin B, and gonadotropins in these men with the results in 24 men with classic GnRH deficiency before and during GnRHreplacement therapy and in 29 normal men of similar age. Results Serum gonadotropin concentrations in the men with adult-onset GnRH deficiency were similar before and during pulsatile GnRH administration to those in the men with classic GnRH deficiency. However, as compared with men with classic GnRH deficiency, men with adult-onset hypogonadotropic hypogonadism had larger mean ( � SD) testicular volumes (18 � 5 vs. 3 � 2 ml, P � 0.001), serum testosterone concentrations (78 � 34 vs. 49 � 20 ng per deciliter [2.7 � 1.2 vs. 1.7 � 0.7 nmol per liter], P � 0.004), and serum inhibin B concentrations (119 � 52 vs. 60 � 21 pg per milliliter, P � 0.001). Treatment with GnRH reversed the hypogonadism and restored fertility in each of the five men who received long-term therapy. Conclusions The recognition of adult-onset hypogonadotropic hypogonadism in men as a distinct disorder expands the spectrum of GnRH deficiency and identifies a treatable form of male infertility. (N Engl J Med 1997;336:410-5.) ©1997, Massachusetts Medical Society.

Long-term administration of pulsatile gonadotropin-releasing hormone for exploration of pituitary functionality in amenorrheic patients

Differentiation between hypothalamic and pituitary amenorrhea is generally based on the luteinizing hormone-releasing hormone (LHRH) test (whether as a single dose, two consecutive doses, or pulsatile over 5- 10 days), together with high-resolution imaging (computed tomography or magnetic resonance) of the sellar region. Long-term administration of gonadotropin-releasing hormone (GnRH) is generally used only for ovulation induction, and not for diagnostic purposes. Here, wereport the results of long-term administration of GnRH to 19 women initially diagnosed as suffering from hypothalamic amenorrhea on the basis of LHRH testing and computed tomography imaging. During treatment, subjects received 20-μg pulses of GnRH every 90 min, subcutaneously from a portable infusion pump. Fourteen subjects responded (i.e. ovulated) during the first treatment cycle; one subject menstruated but did not ovulate during the first cycle, and then dropped out of the study; the remaining four subjects did not ovulate or menstruate despite at least three treatment cycles. Magnetic resonance imaging of the sellar region of these four subjects revealed pituitary lesions (partially empty sella in three cases, microadenoma in one case) which had not been detected by computed tomography. By contrast, no such abnormalities were detected in the nine responders who agreed to undergo magnetic resonance imaging. These findings suggest that long-term administration ojGnRHis of value not onlyforovulation induction but also for diagnostic purposes. Specifically, an initial diagnosis of hypothalamic amenorrhea is confirmed if there is a positive ovulation response after two GnRH treatment cycles; otherwise, pituitary amenorrhea should be suspected. Our results also suggest that magnetic resonance imaging is more effective than computed tomography for the detection of partially empty sella.

Inhibin B secretion in males with gonadotropin-releasing hormone (GnRH) deficiency before and during long-term GnRH replacement: relationship to spontaneous puberty, testicular volume, and prior treatment--a clinical research center study.

To evaluate the physiology of inhibin B in the human male, we measured serum concentrations in normal adult men and men with isolated GnRH deficiency before and during long-term replacement with pulsatile GnRH. At baseline, inhibin B levels in the GnRH-deficient men (n = 31) were significantly lower than normal controls (85 +/- 10 pg/mL vs. 239 +/- 14 pg/mL; P < .01) and correlated positively with pretreatment testicular volume (r = .80, P = .001) and a history of spontaneous puberty, suggesting additional maturational influences on the both testicular volume and inhibin B secretion. Pulsatile GnRH administration was associated with significant increases in inhibin B, with levels averaging 108 +/- 7 pg/mL when serum LH, FSH, and T concentrations had reached the normal adult male range (n = 22; P = .02 vs. baseline). Continued GnRH administration for at least an additional year was not associated with further increases in inhibin B concentrations. Throughout the course of long-term pulsatile GnRH replacement, serum FSH levels were negatively correlated with inhibin B concentrations (e.g. r = -.71, P < 0.01; n = 14 treated 12 months after normalization of T). Although inhibin B concentrations did not correlated with sperm density during therapy, rates of fertility were higher in patients with higher baseline levels (inhibin B > or = 60 pg/mL). Increases in serum concentrations of inhibin B occurring during GnRH replacement demonstrate the gonadotropin regulation of gonadal inhibin B secretion. However, the variation in baseline inhibin B levels before GnRH administration suggests an additional gonadotropin-independent level of modulation. The negative correlation between FSH and inhibin B secretion in GnRH-deficient men receiving long-term GnRH replacement is consistent with a putative role of inhibin B in the negative feedback regulation of FSH, although direct confirmation of this role requires further investigation.