Hormone Receptor Gene Mutation Research Articles

Normal intellectual ability and hyperprolactinemia as unique clinical manifestations of congenital hypothyroidism: A case report and review of hypotheses.

Congenital hypothyroidism is the deficiency of thyroid hormone in infants and hyperprolactinemia is frequently observed. Previously reported cases typically involve intellectual disability, highlighting this particular unique case report to the first reported patient demonstrating normal intellectual ability despite experiencing growth and gonad dysfunction. This study aims to present a case and review medical hypotheses related to the patient's condition. A 19-year-old female presented with a chief complaint of irregular menstruation for up to 40 days or not occurring at all. The patient experienced the first menstruation at the age of 16 years old. The patient's height was 133 cm, body weight 40 kg, and body mass index 22.61 kg/m2; other family members were normal. Physical examination showed no abnormalities, and laboratory examination showed suppressed serum free T4 (FT4) level (6.41 pmol/L), elevated thyroid stimulating hormone (TSH) level (333.700 µIU/mL), and elevated prolactin hormone level (32.03 ng/mL). Ultrasound of the thyroid gland found hypoplasia of the left and right thyroid glands. The patient was a college student enrolled in a public national university and had never complained about academic performance throughout the patient's education. The patient was diagnosed with congenital hypothyroidism and hyperprolactinemia. The patient was administered up to 100 µg daily of oral levothyroxine, which improved the patient's menstrual cycles. The patient's delayed diagnosis may be attributed to central congenital hypothyroidism being underdiagnosed. We hypothesized that thyroid-releasing hormone receptor (TRHR) gene mutation might contribute to the underlying cause of hyperprolactinemia and normal intellectual ability of the patient. Further study on the significance of TRHR gene mutations in congenital hypothyroidism is required to improve diagnosis and treatment.

Expression of the anti-Müllerian hormone receptor (AMHR2) in the endometrium of patients with uterine anomalies

BACKGROUND: Uterine anomalies are a cause of female reproductive failure. Originally, malformations of the Mllerian ducts are believed to be the main reason for uterus abnormalities. There is an assumption that anti-Mllerian hormone (AMH) or AMH receptor (AMHR2) gene mutation may lead to alterations in the formation of the Mllerian ducts in female fetuses resulting in uterine anomalies.
 AIM: The aim of this study was to assess the AMHR2 expression in the endometrium of patients with uterine anomalies and a history of reproductive failure.
 MATERIALS AND METHODS: The present study included 112 women, of whom 92 patients were diagnosed with uterine anomalies (main groups): arcuate uterus (n = 30), septated uterus (n = 30), bicornuate uterus (n = 12), unicornuate uterus (n = 10), didelphys uterus (n = 10); and 20 patients had normal uterine anatomy (control group), with the secretory phase (n = 10) and the proliferative phase (n = 10) of menstrual cycle evaluated. Histological and immunohistochemical studies of the endometrium were carried out according to the standard technique with an assessment of AMHR2 marker expression in the biopsy samples.
 RESULTS: The AMHR2 area expression in the endometrial stroma was significantly lower in patients with septated uterus compared to those with arcuate uterus (р 0.001). The same tendency was noted when compared to other uterine anomalies and healthy controls. AMHR2 expression in the endometrial stroma of patients with arcuate uterus was significantly higher compared to unicornuate uterus (p 0.05).
 CONCLUSIONS: The data obtained suggest that morphofunctional characteristics of the endometrium in patients with uterine anomalies have no specific pathognomonic features. The decline in AMHR2 expression in the endometrial stroma seems to be related to chronic endometritis, as an inverse correlation exists between the AMHR2 area expression and chronic endometritis, compromising pregnancy occurrence.

Analysis of thyroid stimulating hormone receptor gene mutation in children with hyperthyroidism

Objective To explore the characterization of thyroid stimulating hormone receptor(TSHR) gene mutational spectrum in children with hyperthyroidism from Guangzhou. Methods Ninety children were diagnosed with hyperthyroidism from July 2009 to July 2014 in our institute. Their median age at diagnosis was(7.5±3.4) years, and there were 28 males and 62 females. Mutational analysis were performed by performing polymerase chain reaction(PCR) and DNA direct sequencing of exon 10 of TSHR gene. TSHR gene mutations from 50 unrelated healthy children were served as controls. The correlation between TSHR gene and hyperthyroidism in children was explored. Results A total of 3 mutations were identified in ninety children who were diagnosed with hyperthyroidism, one synonymous mutations(p.V614V), and two missense mutations(p.R707W and p. D727E). Mutation of p. V614V do not change amino acid and do not influence the structure and function of TSHR, no pathogenicity. p. R707W is a SNP associated with human cancers. The frequency of C allele of the D727E in children with hyperthyroidism was 86.7%, while 55.0% in the controls, significant different between the children with hyperthyroidism and the controls(P<0.01). In this study, a very high association between the D727E SNP and hyperthyroidism(OR=18.86, P<0.01) was found. Conclusion Three different mutations of TSHR gene exon 10 were identified in 90 children with hyperthyroidism, (c.1842A>G, p.V614V、c.2119C>T, p.R707W、c.2181G>C, p.D727E), there were association between p. D727E and hyperthyroidism, nor p. V614V and p. R707W. Finally, p. D727E may be correlated with hyperthyroidism in children. Key words: Hyperthyroidism; Children; Thyroid stimulating hormone receptor(TSHR); Gene; Mutation

The relationship between follice-stimulating hormone and its receptor in male reproduction

Follicle stimulating hormone (FSH) is the key endocrine hormone regulating the gonadal function of both sexes. FSH stimulates male testicular Sertoli differentiation, promotes testicular development, and mitosis of spermatogonia. FSH maintains adult Sertoli cell metabolism and plays an important role in spermatogenesis, germ cell survival and male fertility. FSH and follicle-stimulating hormone receptor (FSHR) gene mutation or gene polymorphism may affect the role of FSH on target organs. This article reviews the relationship between FSH and FSHR and male reproductive relationship. Key words: Follicle stimulating hormone; Receptors, FSH; Fertility; Men; Review

Spontaneous Ovarian Hyperstimulation Syndrome with FSH Receptor Gene Mutation: Two Rare Case Reports

Development of ovarian hyperstimulation syndrome (OHSS) is very rare in a spontaneous ovulatory cycle and it is usually seen during pregnancy. In the etiology of OHSS, higher hCG (molar pregnancies or multiple pregnancies) and thyroid-stimulating hormone (TSH) levels have been accused. In recent years, some follicle-stimulating hormone (FSH) receptor (FSHR) gene mutations have been described in patients with OHSS in the first trimester with normal hCG levels. Herein, we report two cases of FSHR gene mutation during the investigation of the etiology of spontaneous OHSS. Although OHSS is typically associated with ovulation induction, it should be kept in mind that this condition may also develop in spontaneous pregnancies.

Identification of Functional Thyroid Stimulating Hormone Receptor and TSHR Gene Mutations in Hepatocellular Carcinoma.

Extra-thyroid expression of thyroid stimulating hormone (TSH) receptor (TSHR) has been reported in normal liver tissues, but never assessed in hepatocellular carcinoma (HCC). Paired cancerous and non-cancerous HCC tissues were analyzed with TSHR expression assays. TSHR functional assessments and sequence analysis for the TSHR exon-10 were performed. TSHR overexpression was found in 150/197 (76.1%) HCCs. Higher TSHR expression was associated with unfavorable postoperative outcomes. Immunohistochemical analysis revealed predominantly nuclei/peri-nuclei localization of TSHR in cancerous tissues but cell membrane localization in non-cancerous parts. TSH stimulation on hepatoma cells resulted in increased cyclic adenosine monophosphate levels with altered cell sensitivity to cisplatin. Gene mutations leading to TSHR truncation were detected in 8/81 (9.9%) HCC tissues. Overexpression of TSHR was found in a great majority of HCC tissues and associated with unfavorable prognosis. Cell-based experiments and gene mutation analysis suggested that TSHR in HCCs was functional.

Cancer risk and clinicopathological characteristics of thyroid nodules harboring thyroid-stimulating hormone receptor gene mutations.

Thyroid-stimulating hormone receptor (TSHR) gene mutations play a critical role in thyroid cell proliferation and function. They are found in 20%-82% of hyperfunctioning nodules, hyperfunctioning follicular thyroid cancers (FTC), and papillary thyroid cancers (PTC). The diagnostic importance of TSHR mutation testing in fine needle aspiration (FNA) specimens remains unstudied. To examine the association of TSHR mutations with the functional status and surgical outcomes of thyroid nodules, we evaluated 703 consecutive thyroid FNA samples with indeterminate cytology for TSHR mutations using next-generation sequencing. Testing for EZH1 mutations was performed in selected cases. The molecular diagnostic testing was done as part of standard of care treatment, and did not require informed consent. TSHR mutations were detected in 31 (4.4%) nodules and were located in exons 281-640, with codon 486 being the most common. Allelic frequency ranged from 3% to 45%. Of 16 cases (12 benign, 3 FTC, 1 PTC) with surgical correlation, 15 had solitary TSHR mutations and 1 PTC had comutation with BRAF V600E. Hyperthyroidism was confirmed in all 3 FTC (2 overt, 1 subclinical). Of 5 nodules with solitary TSHR mutations detected at high allelic frequency, 3 (60%) were FTC. Those at low allelic frequency (3%-22%) were benign. EZH1 mutations were detected in 2 of 4 TSHR-mutant malignant nodules and neither of 2 benign nodules. We report that TSHR mutations occur in ∼5% thyroid nodules in a large consecutive series with indeterminate cytology. TSHR mutations may be associated with an increased cancer risk when present at high allelic frequency, even when the nodule is hyperfunctioning. Benign nodules were however most strongly correlated with TSHR mutations at low allelic frequency.

Abstract PD8-07: Identifying steroid hormone receptor gene mutations in patients with newly diagnosed estrogen receptor positive metastatic breast cancer

Abstract Background: Resistance to endocrine therapy remains a challenge for patients with metastatic hormone receptor positive breast cancer. Mutations in the gene encoding estrogen receptor alpha (ESR1) have been identified in patients with endocrine resistance and correlates with reduced survival. The occurrence of mutations in the gene for progesterone receptor (PGR), another important biomarker in breast cancer, has not been reported. Objective: Determine the frequency of mutations in ESR1 and PGR in patients with newly diagnosed metastatic ER+ breast cancer treated with adjuvant endocrine therapy at our institution, and identify whether these mutations are associated with worse patient survival. Methods: This is an IRB-approved, HIPAA-compliant retrospective study of patients with ER+ metastatic breast cancer identified from our comprehensive cancer center registry. Eligible patients must have received at least 6 months of adjuvant endocrine therapy with biopsy-proven diagnosis of metastatic or locally recurrent disease. Next-generation sequencing of the coding regions of ESR1 and PGR was performed on extracted tumor genomic DNA. Analysis was limited to protein coding mutations. Clinicopathologic data was collected and correlated with the genomic information for each patient. Associations between mutation status and clinicopathologic factors were analyzed using Fisher's exact test. Kaplan-Meier method with log-rank test was used to analyze overall survival (OS) from time of metastatic diagnosis. Results: The study included 35 women (35-88 yr old). Metastatic sites included bone (N=13), brain (N=6), chest wall (N=2), liver (N=4), lung/pleura (N=4), and lymph nodes (N=6). PGR mutations were identified in 66% of patients (23/35; 95%CI 48-81%), and were more common than ESR1 mutations (10/35; 29%; 95%CI 15-46%). Mutations in both PGR and ESR1 were identified in 26% (9/35), and neither mutation was identified in 31% (11/35). Neither mutation was associated with prior adjuvant aromatase inhibitor or tamoxifen therapy. There was no significant association between ESR1 or PGR mutations and metastatic site, although 75% (3/4) of patients with liver metastases had an ESR1 mutation compared to 23% (7/31) without liver metastases (p=0.061). The differences in median OS between ESR1 wildtype vs mutant (1.6 mo vs 1.0 mo, p=0.14) and PGR wildtype vs mutant (2.6 mo vs 1.3 mo, p=0.56) were not significant. However, patients with both mutations may have worse median OS compared patients with neither or only one mutation (1.0 mo vs 1.6 mo vs 4.0 mo, p = 0.073). Conclusions: The overall survival of metastatic ER+ breast cancer patients with ESR1 or PGR mutations were not statistically significant compared with those without mutations. Despite the small sample size, there is a trend that patients with mutations in both genes may have worse survival. To the best of our knowledge, the PGR mutation rate in metastatic breast cancer has not previously been reported. Interestingly in our data set, PGR mutations were identified more commonly than mutations in ESR1. The significance of PGR mutations is not known, nor whether this could be a future indicator of treatment resistance or a target for therapy. Citation Format: Fowler AM, Rassman S, DeGrave M, Ong I, Powers GL, Salem K, Kumar M, Woo K, Mahajan AM. Identifying steroid hormone receptor gene mutations in patients with newly diagnosed estrogen receptor positive metastatic breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD8-07.

, , , ,

, , , ,

Clinical, Endocrine, and Molecular Genetic Analysis of a Large Cohort of Saudi Arabian Patients with Laron Syndrome

Background/Aims: Laron syndrome (LS) is an autosomal recessive disease characterized by marked short stature and very low serum IGF-1 and IGFBP-3 levels. This study assessed the clinical and endocrine features alongside determining the growth hormone receptor gene (GHR) mutation in Saudi Arabian patients with LS in order to establish whether or not a genotype/phenotype correlation is evident in this large cohort. Subjects and Methods: A total of 40 Saudi Arabian patients with a suspected diagnosis of LS were recruited and subjected to a full clinical and endocrine investigation together with direct sequencing of the coding regions of the GHR gene. Results: GHR mutations were identified in 34 patients from 22 separate nuclear families. All 34 molecularly confirmed patients had the typical clinical and endocrinological manifestations of LS. Eleven different mutations (9 previously unreported) were detected in this cohort of patients, all inherited in an autosomal recessive homozygous form. No genotype/phenotype correlation was apparent. Conclusion: The identification of pathogenic mutations causing LS will be of tremendous use for the molecular diagnosis of patients in Saudi Arabia and the region in general, with respect to prevention of this disease in the forms of future carrier testing, prenatal testing, premarital screening and preimplantation genetic diagnosis.

The origin of the p.E180 growth hormone receptor gene mutation

Laron syndrome, an autosomal recessive condition of extreme short stature, is caused by the absence or dysfunction of the growth hormone receptor. A recurrent mutation in the GHR gene, p.E180, did not alter the encoded amino acid, but activated a cryptic splice acceptor resulting in a receptor protein with an 8-amino acid deletion in the extracellular domain. This mutation has been observed among Sephardic Jews and among individuals in Ecuador, Brazil and Chile, most notably in a large genetic isolate in Loja, Ecuador. A common origin has been postulated based on a shared genetic background of markers flanking this mutation, suggesting that the Lojanos (and others) may have Sephardic (Converso) Jewish ancestry. Analysis of the population structure of Lojanos based on genome-wide analysis demonstrated European, Sephardic Jewish and Native American ancestry in this group. X-autosomal comparison and monoallelic Y chromosomal and mitochondrial genetic analysis demonstrated gender-biased admixture between Native American women and European and Sephardic Jewish men. These findings are compatible with the co-occurrence of the Inquisition and the colonization of the Americas, including Converso Jews escaping the Inquisition in the Iberian Peninsula. Although not found among Lojanos, Converso Jews also brought founder mutations to contemporary Hispanic and Latino populations in the BRCA1 (c.68_69delAG) and BLM (c.2207_2212delATCTGAinsTAGATTC) genes.

Older individuals heterozygous for a growth hormone-releasing hormone receptor gene mutation are shorter than normal subjects.

Growth hormone (GH)-releasing hormone (GHRH) is the most important stimulus for GH secretion by the pituitary gland. Subjects homozygous for GHRH receptor (GHRHR) gene (GHRHR) inactivating mutations have severe GH deficiency, resulting in severe short stature if not treated. We previously reported that young adults heterozygous for the c.57+1G>A null GHRHR mutation (MUT/N) have reduced weight and body mass index (BMI) but normal stature. Here we have studied whether older MUT/N have an additional phenotype. In a cross-sectional study, we measured height, weight and blood pressure, and calculated BMI in two groups (young, 20-40 years of age) and old (60-80 years) of individuals heterozygous for the same GHRHR mutation, and compared with a large number of individuals of normal genotype residing in the same geographical area. Standard deviation score (SDS) of weight was lower, and BMI had a trend toward reduction in young heterozygous compared with young normals, without significant difference in stature. Conversely, SDS of height was lower in older heterozygous individuals than in controls, corresponding to a reduction of 4.2 cm. These data show a reduced stature in older subjects heterozygous for the c.57+1G>A GHRHR mutation, indicating different effects of heterozygosis through lifespan.

Novel growth hormone-releasing hormone receptor gene mutations in Turkish children with isolated growth hormone deficiency.

Objective: Isolated growth hormone deficiency (IGHD) is defined as a medical condition associated with growth failure due to insufficient production of GH or lack of GH action. Mutations in the gene encoding for GH-releasing hormone receptor (GHRHR) have been detected in patients with IGHD type IB. However, genetic defects on GHRHR causing IGHD in the Turkish population have not yet been reported. To identify mutations on GHRHR gene in a population of Turkish children with IGHD.Methods: Ninety-six Turkish children with IGHD were included in this study. Exon1-13 and exon/intron boundaries of GHRHR were amplified by suitable primers. The polymerase chain reaction products for GHRHR gene were sequenced with primers.Results: We analyzed the GHRHR gene for mutations in ninety-six patients with IGHD based on sequence results. We identified novel p.K264E, p.S317T, p.S330L, p.G369V, p.T257A and C base insertion on position 380 (c.380inserC) mutations. In 5 of the patients, the mutation was homozygote and in 1-heterozygote (p.S317T).Conclusion: Six new missense mutations and one first case of insertion mutations for the GHRHR gene are reported.

Identification and functional analysis of novel human growth hormone-releasing hormone receptor (GHRHR) gene mutations in Japanese subjects with short stature

Growth hormone-releasing hormone receptor (GHRHR) gene mutations have been identified in patients of different ethnic origins with isolated GH deficiency (IGHD) type IB. However, the prevalence of these mutations in the Japanese population has yet to be fully determined. This study aimed to evaluate the contributions of GHRHR mutations to the molecular mechanism underlying short stature in Japanese subjects. The GHRHR gene was sequenced in 127 unrelated Japanese patients with either IGHD (n = 14) or idiopathic short stature (ISS; n = 113). Sequence variants were evaluated in family members and 188 controls, and then examined in functional studies. A novel homozygous E382E (c.1146G>A) synonymous variant, at the last base of exon 12, was identified in an IGHD family with two affected sisters. In vitro splicing studies showed this mutation to result in skipping of exon 12. In one ISS patient, a heterozygous ATG-166T>C variant was found in the distal Pit-1 P2 binding element of the GHRHR promoter. In two control subjects, a close but distinct variant, ATG-164T>C, was detected. Functional studies showed that both promoter variants diminish promoter activity by altering Pit-1 binding ability. Four missense variants were also found in both patient and control groups but had no detectable functional consequences. The homozygous GHRHR mutation was rare, being detected in only one Japanese IGHD family. Future research is needed to clarify the genetic contributions of heterozygous functional promoter variants to GHD, ISS and normal-stature variations.

A Child with Resistance to Thyroid Hormone without Thyroid Hormone Receptor Gene Mutation: A 20-Year Follow-Up

We report here the 20-year follow-up study of a male subject diagnosed at 15 months of age as a sporadic case of pituitary resistance to thyroid hormone on the combination of clinical hyperthyroidism, elevated serum thyroid hormone (TH) levels and inappropriate thyrotropin (TSH). On D-thyroxine (D-T(4)) therapy from 30 months of age to 12.5 years, hyperactivity and hyperthyroid signs and symptoms as well as growth abnormalities improved, serum L-thyroxine (L-T(4)) enantiomer normalized, and basal and stimulated TSH decreased significantly without complete suppression. After 8 years off D-T(4), at 20 years of age, clinical status was normal despite persisting high TH levels and inappropriate TSH. Evolution of serum markers of TH action and echocardiography measurements followed up from 15 months to 20 years of age either in basal condition or on triiodothyronine (T(3)), as well as the sequential determination of bone mineral density suggest differences in the tissue responses to T(3): normal in bone with a high remodelling rate, heterogeneity for various hepatic markers, and decreased at heart level. No mutations were found in the coding sequence of TRbeta1, TRbeta2, TRalpha1, RXRgamma, SMRT, NCoR1, and NCoA1. In this patient the putative long-term effects of the persisting high bone resorption are unknown.

Growth hormone receptor gene mutations in two Italian patients with Laron Syndrome

Laron Syndrome (LS) represents a condition characterized by GH insensitivity caused by molecular defects in the GH receptor (GHR) gene or in the post-receptor signalling pathway. We report the molecular characterization of two unrelated Italian girls from Sicily diagnosed with LS. The DNA sequencing of the GHR gene revealed the presence of different nonsense mutations, occurring in the same background haplotype. The molecular defects occurred in the extracellular domain of the GHR leading to a premature termination signal and to a truncated non-functional receptor. In one patient, a homozygous G to T transversion, in exon 6, led to the mutation GAA to TAA at codon 180 (E180X), while in the second patient a homozygous C to T transition in exon 7 was detected, causing the CGA to TAA substitution at codon 217 (R217X). Both probands presented the polymorphisms Gly168Gly and Ile544Leu in a homozygous state in exons 6 and 10, respectively. The E180X represents a novel defect of the GHR gene, while the R217X mutation has been previously reported in several patients from different ethnic backgrounds but all from countries located in the Mediterranean and Middle Eastern region.

Follicle-Stimulating Hormone Receptor Gene Mutations Are Not Evident in Greek Women with Premature Ovarian Failure and Poor Responders

Background/Aims: This clinical and molecular study aimed to investigate the presence of follicle-stimulating hormone (FSH) receptor gene mutations in women with premature ovarian failure (POF) and poor responders to in vitro fertilization treatment. Methods: DNA was extracted from blood samples for subsequent polymerase chain reaction (PCR). PCR was followed by restriction fragment length polymorphism and direct sequencing. Results: No inactivating mutations reported so far were identified in exons 6, 7, and 10 in women with POF and poor responders. Conclusion: FSH receptor gene mutations are not frequent in Greek patients with POF as is the case in the rest of the world except for cases with ovarian dysgenesis in Finland.

Growth Hormone Releasing Hormone Receptor (GHRH-R) Gene Mutation in Indian Children with Familial Isolated Growth Hormone Deficiency: A Study from Western India

Various mutations of the growth hormone releasing hormone receptor (GHRH-R) gene have been recently described to cause familial isolated growth hormone (GH) deficiency (FIGHD), with the GHRH-R nonsense mutation E72X reported in patients with FIGHD from South Asia. The molecular genetic basis of FIGHD in Indian children is not known. To look for the GHRH-R E72X non-sense mutation in our patients with FIGHD and describe its clinical phenotype. A total of 31 patients from 22 families diagnosed 4-20 years previously, 20 patients with familial IGHD-IB from 11 families and 11 patients with non-familial isolated GH deficiency (NFIGHD) (phenotypes IGHD-IB in eight patients and -IA in three) were included. Twenty-eight of 31 patients with IGHD-IB came from two states of Western India, 27 of them Hindus from 18 families (three consanguineous) and one from an inbred Moslem kindred. Twenty-two of the patients (71%) (18 FIGHD and four NFIGHD) had a homozygous G-->T transversion in exon 3, with this GHRH-R gene mutation E72X in 90% (18/20) of patients with FIGHD, 36% (4/11) of NFIGHD, altogether 78% (22/28) with phenotype IB. One parent pair with IGHD had homozygous E72X mutation, the rest were heterozygous carriers. Two siblings with IGHD due to homozygous E72X mutation were also heterozygous carriers for GH-1 gene 6.7 kb deletion, inherited from their mother, heterozygous for both GH-1 and GHRH-R mutations. Initial chronological age was 10.89 +/- 3.69 years, bone age 6.4 +/- 3.4 years, and mean height SDS was -5.83 +/- 1.41. The clinical phenotype, with sharp features, lean habitus, lack of frontal bossing or hypoglycemia, was characteristic. The mean peak GH was 1.25 +/- 0.75 ng/ml, IGF-I and IGFBP-3 below -2 SDS with no response to GHRH in those tested. MRI (n = 10) showed pituitary hypoplasia, mean vertical height 2.61 +/- 0.76 mm. Among the other 7/11 NFIGHD patients, four with phenotype IB were negative for genotypes tested in this study; of three patients with phenotype IA, two had the GH-1 gene 6.7 kb deletion, and one was a compound heterozygote with 6.7 and 7.6 kb deletions. The majority of patients with FIGHD from different communities belonged to non-consanguineous Hindu families from Western India. The GHRH-R gene E72X mutation was found in 71% of this series, in 90% of FIGHD, 36% of NFIGHD, and in 78% with phenotype IB. The characteristic phenotype helped in suspecting this mutation. GHRH-R gene mutations may be the most reasonable candidate for IGHD-IB with the E72X mutation predominating in the Indian subcontinent. More extensive studies need to be undertaken.

A Novel Mouse Model of Hypogonadotrophic Hypogonadism: N-Ethyl-N-Nitrosourea-Induced Gonadotropin-Releasing Hormone Receptor Gene Mutation

An autosomal-recessive mutation that causes hypogonadotrophic hypogonadism was isolated during an N-ethyl-N-nitrosourea mutagenesis screen in mice. Affected males had micropenis and small, undescended testes with spermatogenesis arrested at the pachytene stage of meiosis, leading to sterility. Androgen-sensitive organs were small and immature. Affected females were externally normal but sterile with small ovaries due to an arrest at the secondary stage of folliculogenesis, and the uterus and oviducts were thin and immature. Circulating reproductive hormones were significantly decreased in affected males and females. There was also a dramatic reduction in the numbers of FSH- and LH-producing gonadotrophs. Meiotic mapping of the mutation and candidate gene sequencing determined that the N-ethyl-N-nitrosourea-induced lesion is in the third transmembrane domain of the GnRH receptor gene (Gnrhr). In vitro studies indicate that the mutant receptor is not coupled to the plasma membrane signal transduction system. Moreover, this mutant cannot be rescued with defined GnRH receptor pharmacoperones (pharmacological chaperones), an approach that rescues many other misfolded mutants. The mutant GnRH receptor was also shown to exert a dominant-negative effect on wild-type receptor function, indicating that the mutant receptor is unable to fold properly and likely misrouted within the cell, not reaching the plasma membrane. Surprisingly, Gnrhr mutant transcripts were significantly up-regulated in the pituitaries of Gnrhr mutants, revealing a previously unknown autoregulatory feedback loop. This is the first report of a mouse with a Gnrhr loss of function mutation. These GnRH-insensitive mice provide a novel animal model for the study of human idiopathic hypogonadotrophic hypogonadism.

Isolated growth hormone deficiency in Chilean patients: clinical and molecular analysis.

Isolated growth hormone deficiency (IGHD) is a disorder that leads to short stature. It has been classified into types IA, IB, II and III. GH gene mutations and growth hormone releasing hormone (GHRH) receptor gene mutations have been described in patients with IGHD. We report here a clinical and molecular study of 27 Chilean patients with IGHD. We performed GH stimulation tests with GHRH and GHRP, and segregation and molecular analysis of the GH, GHRH and GHRH receptor genes. We describe four patients with IGHD IA bearing a 7 kb mutation (13%), and two IGHD II patients who showed two different splice site point mutations (6.8%). In 21 patients, we did not find a mutation in any of the three genes examined. These results led us to conclude that the molecular causes of IGHD involve other genes besides those analyzed in this report, as has been reported previously in patients of different ethnic origins.