Compromised Volumetric Bone Density and Microarchitecture in Men With Congenital Hypogonadotropic Hypogonadism.

CONTEXT: Men with congenital hypogonadotropic hypogonadism (CHH) and Kallmann syndrome (KS) have both low circulating testosterone and estradiol levels. Whether bone structure is affected remains unknown. OBJECTIVE: To characterize bone geometry, volumetric density and microarchitecture in CHH/KS. METHODS: This cross-sectional study, conducted at a single French tertiary academic medical center, included 51 genotyped CHH/KS patients and 40 healthy volunteers. Among CHH/KS men, 98% had received testosterone and/or combined gonadotropins. High-resolution peripheral quantitative computed tomography (HR-pQCT), dual-energy x-ray absorptiometry (DXA), and measurement of serum bone markers were used to determine volumetric bone mineral density (vBMD) and cortical and trabecular microarchitecture. RESULTS: CHH and controls did not differ for age, body mass index, and levels of vitamin D and PTH. Despite long-term hormonal treatment (10.8 ± 6.8 years), DXA showed lower areal bone mineral density (aBMD) in CHH/KS at lumbar spine, total hip, femoral neck, and distal radius. Consistent with persistently higher serum bone markers, HR-pQCT revealed lower cortical and trabecular vBMD as well as cortical thickness at the tibia and the radius. CHH/KS men had altered trabecular microarchitecture with a predominant decrease of trabecular thickness. Moreover, CHH/KS men exhibited lower cortical bone area, whereas total and trabecular areas were higher only at the tibia. Earlier treatment onset (before age 19 years) conferred a significant advantage for trabecular bone volume/tissue volume and trabecular vBMD at the tibia. CONCLUSION: Both vBMD and bone microarchitecture remain impaired in CHH/KS men despite long-term hormonal treatment. Treatment initiation during adolescence is associated with enhanced trabecular outcomes, highlighting the importance of early diagnosis.

Growth and Adult Height during Human Growth Hormone Treatment in Chinese Children with Multiple Pituitary Hormone Deficiency Caused by Pituitary Stalk Interruption Syndrome: A Single Centre Study

Objective: The aim was to assess growth velocity (GV) during human recombinant growth hormone (hGH) treatment of children with multiple pituitary hormone deficiency (MPHD) caused by pituitary stalk interruption syndrome (PSIS) and to analyze the characteristics of patients that attained normal adult heights. Methods: Data from 74 (16 female) children with MPHD caused by PSIS with GH, thyroid stimulating hormone, gonadotropin and adrenocorticotropic hormone deficiencies were collected. Subjects were divided into groups: 12 pre-pubescent females (Female-Group) and 36 pre-pubescent males (Male-Group 1). The remaining 22 males were further sub-divided into two groups (Male-Group 2 and Male-Group 3) according to the initiation of gonadotropin replacement treatment, based on bone age and height. Results: No differences in change in height standard deviation score (△HtSDS) and GV were observed at different time points of hGH treatment between the Female-Group and Male-Group 1 (p>0.05). GV was significantly greater in the first year of hGH therapy than in subsequent years: Female-Group p=0.011; Male-Group 1 p<0.001; Male-Group 2 p=0.005; and Male-Group 3 p=0.046. Adult height was achieved by 23 (19 males and 4 females) patients. The total gain in height positively correlated with the GV during the first year (r=0.626, p<0.001). Conclusion: GV during hGH treatment were similar amongst pre-pubescent males and females with MPHD caused by PSIS. GV during the first year of hGH treatment appears to be an effective predictor of final height in patients with MPHD caused by PSIS.

Long-Term Effect of Cranial Radiotherapy on Pituitary-Hypothalamus Area in Childhood Acute Lymphoblastic Leukemia Survivors.

OPINION STATEMENT: Survival rates of childhood cancer have improved markedly, and today more than 80 % of those diagnosed with a pediatric malignancy will become 5-year survivors. Nevertheless, survivors exposed to cranial radiotherapy (CRT) are at particularly high risk for long-term morbidity, such as endocrine insufficiencies, metabolic complications, and cardiovascular morbidity. Deficiencies of one or more anterior pituitary hormones have been described following therapeutic CRT for primary brain tumors, nasopharyngeal tumors, and following prophylactic CRT for childhood acute lymphoblastic leukemia (ALL). Studies have consistently shown a strong correlation between the total radiation dose and the development of pituitary deficits. Further, age at treatment and also time since treatment has strong implications on pituitary hormone deficiencies. There is evidence that the hypothalamus is more radiosensitive than the pituitary and is damaged by lower doses of CRT. With doses of CRT <50 Gy, the primary site of radiation damage is the hypothalamus and this usually causes isolated GH deficiency (GHD). Higher doses (>50 Gy) may produce direct anterior pituitary damage, which contributes to multiple pituitary deficiencies. The large group of ALL survivors treated with CRT in the 70-80-ties has now reached adulthood, and these survivors were treated mainly with 24 Gy, and the vast majority of these patients suffer from GHD. Further, after long-term follow-up, insufficiencies in prolactin (PRL) and thyroid stimulating hormone (TSH) have also been reported and a proportion of these patients were also adrenocoticotrophic hormone (ACTH) deficient. CRT to the hypothalamus causes neuroendocrine dysfunction, which means that the choice of GH test is crucial for the diagnosis of GHD.

ACTH and gonadotropin deficiencies predict mortality in patients treated for nonfunctioning pituitary adenoma: long-term follow-up of 519 patients in two large European centres.

CONTEXT AND OBJECTIVE: Nonfunctioning pituitary adenomas (NFPAs) are the most common subtype of pituitary tumour. Hypopituitarism is observed in NFPAs due to tumour- or treatment-related factors and may increase mortality risk. Here, we analysed the associations of hypopituitarism, hormone replacement and mortality in a large NFPA cohort derived from two large European centres. DESIGN, SETTING AND PARTICIPANTS: Case note review of all patients treated for NFPA in University Hospitals Birmingham and Beaumont Hospital Dublin between 1999 and 2014 was performed. MAIN OUTCOME MEASURES: Clinical presentation, treatment strategies, pituitary function and vitality status were recorded in each patient. A multivariate Cox regression model was used to examine the association between hypopituitarism, hormone replacement and premature mortality. RESULTS: A total of 519 patients were included in the analysis. Median duration of follow-up was 7·0 years (0·5-43). A total of 81 deaths were recorded (15·6%). On multivariate analysis, adrenocorticotropic hormone (ACTH) and gonadotropin (Gn) deficiencies were associated with an increased relative risk of death (OR 2·26, 95% CI 1·15-4·47, P = 0·01 and OR 2·56, 95% CI 1·10-5·96, P = 0·01, respectively). Increased hydrocortisone (HC) (P-trend = 0·02) and lower levothyroxine (LT4) doses (P-trend = 0·03) were associated with increased risk of death. Mortality increased with the degree of pituitary failure observed (P-trend = 0·04). CONCLUSION: ACTH and gonadotropin-deficient patients have higher mortality rates compared to those with intact hormonal axes. Excessive HC and suboptimal LT4 replacement may also increase risk of death. Complex associations between hormone deficiency and replacement underpin the increased mortality risk in NFPA patients.

Development of additional pituitary hormone deficiencies in pediatric patients originally diagnosed with isolated growth hormone deficiency due to organic causes.

OBJECTIVE: To determine characteristics of children initially diagnosed with isolated growth hormone deficiency (IGHD) of organic aetiology, who later developed multiple pituitary hormone deficiencies (MPHD). DESIGN: Data were analysed for 716 growth hormone-treated children with organic IGHD, who were growth hormone-naïve at baseline in the multinational, observational Genetics and Neuroendocrinology of Short Stature International Study. METHODS: Development of MPHD was ascertained from investigator-provided diagnoses, adverse events and concomitant medications. Analyses were performed for all patients and separately for those who developed MPHD within 4.5 years or had >3.5 years follow-up and continued to have IGHD (4-year cohort). RESULTS: MPHD developed in 71/716 (9.9%) children overall, and in 60/290 (20.7%) in the 4-year cohort. The most frequent additional deficiencies were thyroid-stimulating hormone (47 patients) and gonadotropins (23 patients). Compared with those who remained with IGHD, children who developed MPHD had more severe GHD at study entry, significantly lower baseline insulin-like growth factor1, peak stimulated growth hormone, and more frequent diagnosis of intracranial tumour or mutation of gene(s) controlling hypothalamic-pituitary development and/or function. Multivariate logistic regression analyses identified female gender, longer follow-up, higher baseline age and lower peak stimulated growth hormone as predictors of MPHD development. CONCLUSIONS: MPHD is more likely to develop in patients with severe organic IGHD, especially those with history of intracranial tumour or mutation of gene(s) controlling hypothalamic-pituitary development and/or function. Older baseline age, female gender and longer follow-up duration were also associated with higher incidence of MPHD. Long-term monitoring of pituitary function is recommended, irrespective of the aetiology of GHD.

Genetics of Hypogonadotropic Hypogonadism.

Hypogonadotropic hypogonadism (HH) often manifests as pubertal delay. A considerable proportion of cases of HH is due to genetic mutations. Recognizing those mutated genes and associated phenotypes may improve our diagnostic capabilities. GNRHR and TACR3 should be the first two genes to be screened in a clinical setting for equivocal cases such as constitutional delay in puberty versus idiopathic HH. In Kallmann syndrome (KS), according to the presence of certain accompanying clinical features, genetic screening for particular gene(s) may be prioritized: synkinesia (KAL1), dental agenesis (FGF8/FGFR1), bony anomalies (FGF8/FGFR1), and hearing loss (CHD7, SOX10). FEZF1 has recently been added to the growing list of KS genes. Also, discovery of mutations in KISS1/KISS1R and TAC3/TACR3 in kisspeptin and neurokinin B signaling, respectively, has provided major advancements in our understanding of the biology of the gonadotropin-releasing hormone pulse generator. Identification of further causative mutations accounting for the HH phenotype, which is now more feasible with the increasing popularity of whole exome sequencing, may provide deeper insight into the biology of the hypothalamic-pituitary-gonadal axis.

Role of Gonadotropin-releasing Hormone Stimulation Test in Diagnosing Gonadotropin Deficiency in Both Males and Females with Delayed Puberty.

BACKGROUND: Delayed puberty can result either from constitutional delay of growth and puberty (CDP) or idiopathic hypogonadotropic hypogonadism (IHH). Gonadotropin-releasing hormone (GnRH) stimulation test has been generally accepted as a current method for diagnosing delayed puberty. The objective of this research was to assess the cut-off values and the efficacy of GnRH stimulation test in the diagnosis of delayed puberty in both males and females. METHODS: A study of 91 IHH, 27 CDP patients, 6 prepubertal children, and 20 pubertal adults was undertaken. Blood samples were obtained at 0, 30, 60, and 120 min after GnRH administration and the levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured. For each parameter, the sensitivities and specificities were estimated, and the receiver operating characteristic (ROC) curves were constructed. RESULTS: The ROC curves indicated that a serum basal LH <0.6 IU/L or peak LH <9.74 IU/L resulted in moderate sensitivity (73.8% or 80.0%) and specificity (90.9% or 86.4%) in the diagnosis of HH in males. Serum basal LH <0.85 IU/L or basal FSH <2.43 IU/L resulted in moderate sensitivity (80.0% or 100.0%) and specificity (75.0% or 50.0%) in the diagnosis of HH in females. CONCLUSIONS: Our data suggest that isolated use of the gonadorelin stimulation test is almost sufficient to discriminate between HH and CDP in males, but unnecessary in females. The most useful predictor is serum basal or peak LH to differentiate these two disorders in males, but serum basal LH or FSH in females.

Relationship between pituitary stalk (PS) visibility and the severity of hormone deficiencies: PS interruption syndrome revisited.

CONTEXT: Pituitary stalk interruption syndrome (PSIS) is a rare cause of combined pituitary hormone deficiency characterized by a triad shown in pituitary imaging, yet it has never been evaluated due to the visibility of pituitary stalk (PS) in imaging findings. OBJECTIVE: The major objective of the study was to systematically describe the disease including clinical presentations, imaging findings and to estimate the severity of anterior pituitary hormone deficiency based on the visibility of the PS. METHODS: This was a retrospective study including 74 adult patients with PSIS in Shanghai Clinical Center for Endocrine and Metabolic Diseases between January 2010 and June 2014. Sixty had invisible PS according to the findings on MRI, while the rest had a thin or intersected PS. Basic characteristics and hormonal status were compared. RESULTS: Of the 74 patients with PSIS, age at diagnosis was 25 (22-28) years. Absent pubertal development (97·3%) was the most common presenting symptom, followed by short stature. Insulin tolerance test (ITT) and gonadotrophin-releasing hormone (GnRH) stimulation test were used to evaluate the function of anterior pituitary. The prevalence of isolated deficiency in growth hormone (GH), gonadotrophins, corticotrophin and thyrotrophin were 100%, 97·2%, 88·2% and 70·3%, respectively. Although the ratio of each deficiency did not vary between patients with invisible PS and with visible PS, panhypopituitarism occurred significantly more frequent in patients with invisible PS. Patients with invisible PS had significantly lower levels of luteinizing hormone (LH), follicle stimulation hormone (FSH) and hormones from targeted glands including morning cortisol, 24-h urine free cortisol, free triiodothyronine (FT3), free thyroxine (FT4) and testosterone (T) in male than patients with visible PS. Moreover, patients with invisible PS had lower peak LH and FSH in GnRH stimulation test, and higher peak cortisol in ITT while peak GH remained unchanged between two groups. CONCLUSIONS: The prevalence of multiple anterior pituitary hormone deficiency was high in adult patients with PSIS. And more importantly, we found the visibility of PS shown on MRI might be an indication of the severity of PSIS.

Pituitary dysfunction after aneurysmal subarachnoid haemorrhage: course and clinical predictors­the HIPS study.

OBJECTIVE: We describe the occurrence and course of anterior pituitary dysfunction (PD) after aneurysmal subarachnoid haemorrhage (SAH), and identify clinical determinants for PD in patients with recent SAH. METHODS: We prospectively collected demographic and clinical parameters of consecutive survivors of SAH and measured fasting state endocrine function at baseline, 6 and 14 months. We included dynamic tests for growth-hormone function. We used logistic regression analysis to compare demographic and clinical characteristics of patients with SAH with and without PD. RESULTS: 84 patients with a mean age of 55.8 (±11.9) were included. Thirty-three patients (39%) had PD in one or more axes at baseline, 22 (26%) after 6 months and 6 (7%) after 14 months. Gonadotropin deficiency in 29 (34%) patients and growth hormone deficiency (GHD) in 26 (31%) patients were the most common deficiencies. PD persisted until 14 months in 6 (8%) patients: GHD in 5 (6%) patients and gonadotropin deficiency in 4 (5%). Occurrence of a SAH-related complication was associated with PD at baseline (OR 2.6, CI 2.2 to 3.0). Hydrocephalus was an independent predictor of PD 6 months after SAH (OR 3.3 CI 2.7 to 3.8). PD was associated with a lower score on health-related quality of life at baseline (p=0.06), but not at 6 and 14 months. CONCLUSIONS: Almost 40% of SAH survivors have PD. In a small but substantial proportion of patients GHD or gonadotropin deficiency persists over time. Hydrocephalus is independently associated with PD 6 months after SAH. TRIAL REGISTRATION NUMBER: NTR 2085.

Iatrogenic venous thrombosis secondary to supplemental medicine toxicity.

OBJECTIVE: We described a case of cerebral venous sinus thrombosis in a patient taking multiple supplements as part of a naturopathic anti-aging regimen. METHODS: Case report. RESULTS: The patient presented with a thalamic infarct associated with a thrombus in the vein of Galen. He reported no previous history of endocrinopathy and no known hypercoagulability risk factors. He was treated with therapeutic anticoagulation resulting in improvement. Diagnostic workup revealed hyperthyroidism and gonadotrophic deficiency attributed to significant supplement medicine usage. CONCLUSION: This case highlights a potential risk of dietary supplements. Use of these supplements may be a risk factor for idiopathic cerebral venous thrombosis.

Gonadal function of beta-thalassemics following stem cell transplantation conditioned with myeloablative and reduced intensity regimens.

Gonadal dysfunction is a complication following stem cell transplantation (SCT). There have been no reports of gonadal function in stem-cell-transplanted thalassemic survivors who received a reduced intensity conditioning regimen (RIC). We evaluated gonadal function in 47 ß-thalassemic patients following SCT with either myeloablative or reduced intensity regimen. Thirty-six patients received a myeloablative regimen, the remaining 11 patients had an RIC regimen. Their median (range) age was 13.2 (5.9-25.8) years. There were 29 patients (62%) with gonadal dysfunction (26 with primary gonadal dysfunction and three with gonadotropin deficiency). Comparisons between patients who received myeloablative and RIC regimens, revealed no differences in gonadal dysfunction (56% vs. 82%, p=0.113, respectively). In conclusion, our study demonstrated high frequency of gonadal dysfunction in these patients. Even after receiving RIC, gonadal dysfunction was very common. To our knowledge, this study is the first to report gonadal function in children and adolescents with ß-thalassemia disease who were pre-transplanted with RIC.

Hormone replacement therapy in children with hypogonadotropic hypogonadism: where do we stand?

OBJECTIVE: To characterize hormone replacement therapy in a cohort of adolescent males and females with hypogonadotropic hypogonadism (HH) with a focus on changes in management during the past 10 years. METHODS: Medical records of patients followed for HH during the past 10 years were reviewed. RESULTS: A total of 45 patients (22 female: 23 male) with HH were identified. The average age at HH diagnosis was 14.48 ± 2.02 years in females and 14.89 ± 1.64 years in males (P = .53). In females, the average age of pubertal induction was 14.53 ± 1.86 years. Conjugated equine estrogen was used in 54.5%, transdermal estradiol in 41%, and oral estradiol in 4.5%. The average duration to cycling was 1.96 ± 0.78 years. A progressive increase in the use of transdermal estradiol was noted over time, with 100% of females being started on this regimen since 2008. In males, the average age of induction was 15.22 ± 1.41 years. All were started on intramuscular testosterone cypionate at various doses. The average duration to full adult replacement was 1.95 ± 0.51 years. CONCLUSION: There is no current standard of care to guide pubertal induction in adolescents with HH. However, a significant increase in the use of transdermal estrogen was noted in females during the past 10 years. While much less variability in pubertal induction was seen in males, wide disparities in doses and escalation schedules were found. Prospective studies aimed at elucidating optimal strategies for sex steroid replacement in this pediatric population are badly needed.

Serum insulin-like factor 3 is highly correlated with intratesticular testosterone in normal men with acute, experimental gonadotropin deficiency stimulated with low-dose human chorionic gonadotropin: a randomized, controlled trial.

OBJECTIVE: To study the potential role for using serum biomarkers, including insulin-like factor 3 (INSL3), 17α-hydroxyprogesterone, antimüllerian hormone, and inhibin B, as correlates of intratesticular T (IT-T) concentrations in men. DESIGN: Prospective, randomized, controlled trial. SETTING: University-based medical center. PATIENT(S): Thirty-seven healthy men aged 18-50 years. INTERVENTION(S): All men received the GnRH antagonist acyline, plus very low doses of hCG (0 IU, 15 IU, 60 IU, or 125 IU) SC every other day or 7.5 g T gel daily (75 mg delivered). The IT-T concentrations obtained by percutaneous testicular aspiration with simultaneous serum protein and steroid concentrations were measured at baseline and after 10 days of treatment. MAIN OUTCOME MEASURE(S): Intratesticular and serum hormone and gonadotropin concentrations. RESULT(S): After 10 days of gonadotropin suppression, serum INSL3 decreased by more than 90% and correlated highly with IT-T concentrations. In contrast, serum inhibin B, antimüllerian hormone, and 17α-hydroxyprogesterone did not correlate with IT-T. Serum INSL3 increased with the dose of hCG administered and returned to baseline after treatment. CONCLUSION(S): Serum INSL3 correlates highly with IT-T and serum T concentrations during acute gonadotropin suppression in men. Human chorionic gonadotropin stimulates dose-dependent increases in INSL3 and IT-T in healthy men and might be a useful biomarker of IT-T concentration in some clinical settings. CLINICAL TRIAL REGISTRATION NUMBER: NCT# 00839319.

Altered expression of Alzheimer's disease-related proteins in male hypogonadal mice.

Age-related depletion of estrogens and androgens is associated with an increase in Alzheimer's disease (AD) brain pathology and diminished cognitive function. Here we investigated AD-associated molecular and cellular changes in brains of aged hypogonadal (hpg) male and female mice. hpg Mice have a spontaneous, inactivating genetic mutation in the GnRH gene resulting in life-long deficiency of gonadotropins and gonadal sex hormones. Western blot analysis revealed low levels of amyloid precursor protein and high levels of presenilin 1, amyloid precursor protein C-terminal fragment, and ß-amyloid 42 in brains of aged male, but not female, hpg mice. Changes were confined to the hippocampus and were not evident in the cerebellum or other brain tissues. Male hpg mice tended to have lower levels of IL-1ß protein than male littermate controls. Immunohistochemical staining of the basal forebrain revealed that male hpg mice had lower choline acetyltransferase levels per neuron compared with controls. These AD-like changes specific to male hpg mice supports a link between androgen depletion and the development of AD pathology.

Time course of hypothalamic-pituitary deficiency in adults receiving cranial radiotherapy for primary extrasellar brain tumors.

BACKGROUND: No longitudinal data on hypothalamic-pituitary (HP) function are available in patients who had received cranial radiation therapy (CRT) for primary extrasellar brain tumors (PBT). PURPOSE: To investigate the effects of CRT on HP function in adults with PBT. PATIENTS AND METHODS: Twenty-six adults irradiated for PBT and six CRT naive controls were studied. CRT was delivered with 6 MV X-ray by a linear accelerator (2 Gy fraction schedule). Gross Tumor Volume (GTV) excluded the HP region that was contoured on the planning CT. Median dose to the HP region was 41.8 Gy (IQR: 30.7-49.8). RESULTS: All controls maintained normal HP function. Hypopituitarism developed in 38% of CRT patients (GH deficiency 29%, ACTH 22%, TSH 14%, gonadotropin 4%, no abnormal prolactin level or diabetes insipidus). All HP failures occurred within 32 months after CRT. CONCLUSIONS: Adults undergoing CRT for PBT are at increased risk for HP dysfunction within 3 years from CRT. Endocrine surveillance is recommended also in adults patients exposed to CRT for primary brain tumors distant from HP region.

Animal models for aberrations of gonadotropin action.

During the last two decades a large number of genetically modified mouse lines with altered gonadotropin action have been generated. These mouse lines fall into three categories: the lack-of-function mice, gain-of-function mice, and the mice generated by breeding the abovementioned lines with other disease model lines. The mouse strains lacking gonadotropin action have elucidated the necessity of the pituitary hormones in pubertal development and function of gonads, and revealed the processes from the original genetic defect to the pathological phenotype such as hypo- or hypergonadotropic hypogonadism. Conversely, the strains of the second group depict consequences of chronic gonadotropin action. The lines vary from those expressing constitutively active receptors and those secreting follicle-stimulating hormone (FSH) with slowly increasing amounts to those producing human choriogonadotropin (hCG), amount of which corresponds to 2000-fold luteinizing hormone (LH)/hCG biological activity. Accordingly, the phenotypes diverge from mild anomalies and enhanced fertility to disrupted gametogenesis, but eventually chronic, enhanced and non-pulsatile action of both FSH and LH leads to female and male infertility and/or hyper- and neoplasias in most of the gonadotropin gain-of-function mice. Elevated gonadotropin levels also alter the function of several extra-gonadal tissues either directly or indirectly via increased sex steroid production. These effects include promotion of tumorigenesis in tissues such as the pituitary, mammary and adrenal glands. Finally, the crossbreedings of the current mouse strains with other disease models are likely to uncover the contribution of gonadotropins in novel biological systems, as exemplified by the recent crossbreed of LHCG receptor deficient mice with Alzheimer disease mice.

Genetics defects in GNRH1: a paradigm of hypothalamic congenital gonadotropin deficiency.

Gonadotropin-releasing hormone (GnRH) is a crucial neurohormone regulating puberty and reproduction in non primate mammals, monkeys and humans. This neuropeptide is released in synchronized pulses from the nerve endings of several hundred GnRH neurons into the hypophyseal portal system to stimulate the biosynthesis and secretion of LH and FSH from pituitary gonadotrophs. These two dimeric glycoprotein hormones in turn travel through the circulation to the gonads, stimulating the synthesis and secretion of male and female sex steroid hormones and gametogenesis in both genders. Congenital hypogonadotropic hypogonadism (CHH) is a clinical syndrome that results from a decrease in gonadotropin secretion and is characterized by a complete or partial lack of pubertal development. CHH is caused mainly by defective GnRH production or release by the hypothalamus or by defective GnRH-receptor function in the pituitary. The syndromes of GnRH deficiency, either with anosmia or hyposmia, termed Kallmann Syndrome (KS), or with a normal sense of smell, called normosmic non syndromic CHH, (nCHH) are important disease models that have revealed respectively much about the developmental and functional abnormalities that can befall the GnRH neurons. For more than three decades, GNRH1 was an obvious candidate gene for nCHH in human beings. Indeed, in the natural hpg mouse model discovered in 1977, the hypogonadotropic hypogonadal phenotype, secondary to a hypothalamic GnRH deficiency, was caused by a homozygous deletion within the ortholog Gnrh1 gene. In 2009, homozygous inactivating mutations in the GNRH1 gene causing hypothalamic nCHH patients were at last reported in one female and two young male subjects, validating definitively the pivotal role of GnRH in human pubertal development and reproduction.