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1.
Horm Res Paediatr ; 2024 Jun 28.
Article in English | MEDLINE | ID: mdl-38952118

ABSTRACT

Introduction The clinical features of bi-allelic IGF1 defects are well established, i.e. severe growth failure and microcephaly, delayed psychomotor development, and sensorineural deafness. However, information on clinical and endocrine consequences of heterozygous IGF1 variants and treatment options is scarce. We aimed at extending the knowledge base of the clinical presentation and growth response to recombinant human growth hormone (rhGH) of patients carrying such variants. Methods Retrospective case series of patients with pathogenic heterozygous IGF1 variants. Results Nine patients from six families were included, harbouring five whole or partial gene deletions and one frameshift variant resulting in a premature stop codon (three de novo, one unknown inheritance). In the other two families variants segregated with short stature. Mean (SD) birth length was -1.9 (1.3) SDS (n=7), height -3.8 (0.6) SDS, head circumference -2.5 (0.6) SDS, serum IGF-I -1.9 (0.7) SDS, serum IGFBP-3 1.1 (0.4) SDS (n=7) and GH peak range 5-31 µg/L (n=4). Five patients showed feeding problems in infancy. Average height increased after 1 and 2 years of rhGH treatment by 0.8 SDS (range 0.3-1.3 SDS) and 1.3 SDS (range 0.5-2.0 SDS), respectively. Adult height in two patients was -2.8 and -1.3 SDS, which was respectively 1.3 and 2.9 SDS taller than predicted before start of treatment. Conclusion Haploinsufficiency of IGF1 causes a variable phenotype of prenatal and postnatal growth failure, microcephaly, feeding difficulties, low/low-normal serum IGF-I values in contrast to serum IGFBP-3 in the upper-normal range. Treatment with rhGH increased growth in the first two years of treatment, and in two patients adult height after treatment was higher than predicted at treatment initiation.

2.
Horm Res Paediatr ; : 1-11, 2024 Jun 05.
Article in English | MEDLINE | ID: mdl-38838658

ABSTRACT

INTRODUCTION: The diagnostic yield of genetic analysis in the evaluation of children with short stature depends on associated clinical characteristics, but the additional effect of parental consanguinity has not been well documented. METHODS: This observational case series of 42 short children from 34 consanguineous families was collected by six referral centres of paediatric endocrinology (inclusion criteria: short stature and parental consanguinity). In 18 patients (12 families, group 1), the clinical features suggested a specific genetic defect in the growth hormone (GH) insulin-like growth factor I (IGF-I) axis, and a candidate gene approach was used. In others (group 2), a hypothesis-free approach was chosen (gene panels, microarray analysis, and whole exome sequencing) and further subdivided into 11 patients with severe short stature (height <-3.5 standard deviation score [SDS]) and microcephaly (head circumference <-3.0 SDS) (group 2a), 10 patients with syndromic short stature (group 2b), and 3 patients with nonspecific isolated GH deficiency (group 2c). RESULTS: In all 12 families from group 1, (likely) pathogenic variants were identified in GHR, IGFALS, GH1, and STAT5B. In 9/12 families from group 2a, variants were detected in PCNT, SMARCAL1, SRCAP, WDR4, and GHSR. In 5/9 families from group 2b, variants were found in TTC37, SCUBE3, NSD2, RABGAP1, and 17p13.3 microdeletions. In group 2c, no genetic cause was found. Homozygous, compound heterozygous, and heterozygous variants were found in 21, 1, and 4 patients, respectively. CONCLUSION: Genetic testing in short children from consanguineous parents has a high diagnostic yield, especially in cases of severe GH deficiency or insensitivity, microcephaly, and syndromic short stature.

3.
JCI Insight ; 9(6)2024 Feb 20.
Article in English | MEDLINE | ID: mdl-38516887

ABSTRACT

Silver-Russell syndrome (SRS) is a heterogeneous disorder characterized by intrauterine and postnatal growth retardation. HMGA2 variants are a rare cause of SRS and its functional role in human linear growth is unclear. Patients with suspected SRS negative for 11p15LOM/mUPD7 underwent whole-exome and/or targeted-genome sequencing. Mutant HMGA2 protein expression and nuclear localization were assessed. Two Hmga2-knockin mouse models were generated. Five clinical SRS patients harbored HMGA2 variants with differing functional impacts: 2 stop-gain nonsense variants (c.49G>T, c.52C>T), c.166A>G missense variant, and 2 frameshift variants (c.144delC, c.145delA) leading to an identical, extended-length protein. Phenotypic features were highly variable. Nuclear localization was reduced/absent for all variants except c.166A>G. Homozygous knockin mice recapitulating the c.166A>G variant (Hmga2K56E) exhibited a growth-restricted phenotype. An Hmga2Ter76-knockin mouse model lacked detectable full-length Hmga2 protein, similarly to patient 3 and 5 variants. These mice were infertile, with a pygmy phenotype. We report a heterogeneous group of individuals with SRS harboring variants in HMGA2 and describe the first Hmga2 missense knockin mouse model (Hmga2K56E) to our knowledge causing a growth-restricted phenotype. In patients with clinical features of SRS but negative genetic screening, HMGA2 should be included in next-generation sequencing testing approaches.


Subject(s)
HMGA2 Protein , Silver-Russell Syndrome , Animals , Humans , Mice , Base Sequence , Growth Disorders/genetics , HMGA2 Protein/genetics , Phenotype , Silver-Russell Syndrome/genetics , Silver-Russell Syndrome/diagnosis
4.
Horm Res Paediatr ; 97(1): 11-21, 2024.
Article in English | MEDLINE | ID: mdl-37054683

ABSTRACT

Current clinical guidelines provide information about the diagnostic workup of children with growth failure. This mini-review focuses on the nutritional assessment, which has received relatively little attention in such guidelines. The past medical history, in particular a low birth size and early feeding problems, can provide information that can increase the likelihood of nutritional deficits or several genetic causes. The current medical history should include a dietary history and can thereby reveal a poorly planned or severely restricted diet, which can be associated with nutritional deficiencies. Children on a vegan diet should receive various nutritional supplements, but insufficient compliance has been reported in one-third of cases. While proper use of nutritional supplements in children consuming a vegan diet appears to be associated with normal growth and development, insufficient intake of supplements may impede growth and bone formation. Physical examination and analysis of height and weight over time can help differentiating between endocrine causes, gastrointestinal disorders, psychosocial problems, or underlying genetic conditions that prevent adequate nutritional intake. Laboratory screening should be part of the workup in every child with short stature, and further laboratory tests can be indicated if warranted by the dietary history, especially in children on a poorly planned vegan diet.


Subject(s)
Malnutrition , Nutritional Status , Child , Humans , Diet, Vegetarian , Diet, Vegan , Dietary Supplements , Failure to Thrive/diagnosis
5.
Eur J Endocrinol ; 188(1)2023 Jan 10.
Article in English | MEDLINE | ID: mdl-36651155

ABSTRACT

Idiopathic short stature (ISS) is a diagnosis of exclusion, and therefore each child with short stature or slow growth referred to a paediatrician deserves a full medical history and physical examination, as well as radiological and laboratory screening tests. In patients with an increased likelihood of a genetic cause, genetic testing is indicated. Idiopathic short stature is an approved indication for recombinant human growth hormone (rhGH) in the USA but not in most other parts of the world. In a recent article published in this journal, Luo et al reported on the 1-year's results of a multicentre randomized controlled trial (n = 360) on the efficacy and safety of two dosages of long-acting PEGylated rhGH (PEG-rhGH, Jintrolong®) (0.1 or 0.2 mg/kg body weight per week, respectively) in children with ISS compared with an untreated control group. The growth response to the higher dosage was similar to reported data on daily rhGH. In this commentary, we discuss whether the recent data on genetic causes of short stature in children who initially were labelled ISS, and data on the long-term safety of daily rhGH, may influence the balance between risks and benefits of rhGH treatment in children with ISS. We further discuss the pharmacokinetic and -dynamic profile of PEG-rhGH and its potential consequences for long-term safety.


Subject(s)
Dwarfism , Human Growth Hormone , Humans , Child , Human Growth Hormone/therapeutic use , Growth Hormone , Growth Disorders/diagnosis , Growth Disorders/drug therapy , Dwarfism/diagnosis , Dwarfism/drug therapy , Recombinant Proteins/therapeutic use , Polyethylene Glycols/therapeutic use , Body Height
6.
J Clin Res Pediatr Endocrinol ; 15(4): 431-437, 2023 11 22.
Article in English | MEDLINE | ID: mdl-35466665

ABSTRACT

IGSF1 deficiency is a rare X-linked condition characterized by central hypothyroidism and a wide variety of other clinical features with variable prevalence, including a delayed pubertal testosterone rise and growth spurt in the context of normal or accelerated testicular growth, and adult macroorchidism with relatively low serum testosterone concentrations. Other features include increased waist circumference, attention deficit, prolactin deficiency and transient partial growth hormone (GH) deficiency in childhood, contrasting with an increased GH secretion in adulthood. Patients with this disorder are not detected shortly after birth if neonatal screening programs are based on thyroid-stimulating hormone (TSH) concentrations. A 13.2-year-old male patient was referred to pediatric endocrinology for evaluation of short stature. He was born large for gestational age into a nonconsanguineous family. During work-up for short stature, deficiencies of TSH, prolactin and GH were detected, leading to treatment with levothyroxine and GH. At 16.9 years, GH treatment was stopped and during transition to adult care, his insulin-like growth factor 1 level was above the normal range. This prompted an analysis of IGSF1, in which a novel hemizygous variant causing a stop codon at c.3559C>T (p.Q1187*) was found, confirming the diagnosis of IGSF1 deficiency syndrome. In this report, we describe his clinical and hormonal characteristics at presentation and during long-term follow-up.


Subject(s)
Dwarfism, Pituitary , Hypothyroidism , Transition to Adult Care , Adolescent , Humans , Male , Hypothyroidism/drug therapy , Immunoglobulins , Insulin-Like Growth Factor I , Membrane Proteins , Prolactin , Testosterone , Thyrotropin
7.
Genes (Basel) ; 13(4)2022 03 30.
Article in English | MEDLINE | ID: mdl-35456429

ABSTRACT

In recent years, variants in immunoglobulin superfamily member 1 (IGSF1) have been associated with congenital hypopituitarism. Initially, IGSF1 variants were only reported in patients with central hypothyroidism (CeH) and macroorchidism. Later on, IGSF1 variants were also reported in patients with additional endocrinopathies, sometimes without macroorchidism. We studied IGSF1 as a new candidate gene for patients with combined CeH and growth hormone deficiency (GHD). We screened 80 male and 14 female Dutch patients with combined CeH and GHD for variants in the extracellular region of IGSF1, and we report detailed biomedical and clinical data of index cases and relatives. We identified three variants in our patient cohort, of which two were novel variants of unknown significance (p.L570I and c.1765+37C>A). In conclusion, we screened 94 patients with CeH and GHD and found variants in IGSF1 of which p.L570I could be of functional relevance. We provide detailed phenotypic data of two boys with the p.C947R variant and their large family. The remarkable phenotype of some of the relatives sheds new light on the phenotypic spectrum of IGSF1 variants.


Subject(s)
Hypothyroidism , Immunoglobulins , Female , Growth Hormone , Humans , Hypothyroidism/genetics , Immunoglobulins/genetics , Male , Membrane Proteins/genetics , Mutation , Phenotype
9.
Horm Res Paediatr ; 94(3-4): 81-104, 2021.
Article in English | MEDLINE | ID: mdl-34091447

ABSTRACT

The current differential diagnosis for a short child with low insulin-like growth factor I (IGF-I) and a normal growth hormone (GH) peak in a GH stimulation test (GHST), after exclusion of acquired causes, includes the following disorders: (1) a decreased spontaneous GH secretion in contrast to a normal stimulated GH peak ("GH neurosecretory dysfunction," GHND) and (2) genetic conditions with a normal GH sensitivity (e.g., pathogenic variants of GH1 or GHSR) and (3) GH insensitivity (GHI). We present a critical appraisal of the concept of GHND and the role of 12- or 24-h GH profiles in the selection of children for GH treatment. The mean 24-h GH concentration in healthy children overlaps with that in those with GH deficiency, indicating that the previously proposed cutoff limit (3.0-3.2 µg/L) is too high. The main advantage of performing a GH profile is that it prevents about 20% of false-positive test results of the GHST, while it also detects a low spontaneous GH secretion in children who would be considered GH sufficient based on a stimulation test. However, due to a considerable burden for patients and the health budget, GH profiles are only used in few centres. Regarding genetic causes, there is good evidence of the existence of Kowarski syndrome (due to GH1 variants) but less on the role of GHSR variants. Several genetic causes of (partial) GHI are known (GHR, STAT5B, STAT3, IGF1, IGFALS defects, and Noonan and 3M syndromes), some responding positively to GH therapy. In the final section, we speculate on hypothetical causes.


Subject(s)
Dwarfism, Pituitary , Dwarfism , Human Growth Hormone/metabolism , Insulin-Like Growth Factor I/deficiency , Muscle Hypotonia , Noonan Syndrome , Spine/abnormalities , Child , Child, Preschool , Diagnosis, Differential , Dwarfism/diagnosis , Dwarfism/genetics , Dwarfism/metabolism , Dwarfism, Pituitary/diagnosis , Dwarfism, Pituitary/genetics , Dwarfism, Pituitary/metabolism , Human Growth Hormone/genetics , Humans , Insulin-Like Growth Factor I/metabolism , Muscle Hypotonia/diagnosis , Muscle Hypotonia/genetics , Muscle Hypotonia/metabolism , Noonan Syndrome/diagnosis , Noonan Syndrome/genetics , Noonan Syndrome/metabolism , Spine/metabolism
10.
J Endocr Soc ; 5(4): bvab023, 2021 Apr 01.
Article in English | MEDLINE | ID: mdl-33796801

ABSTRACT

Loss-of-function mutations in the X-linked immunoglobulin superfamily, member 1 (IGSF1) gene result in central hypothyroidism, often associated with macroorchidism. Testicular enlargement in these patients might be caused by increases in follicle-stimulating hormone (FSH) levels, as IGSF1 has been proposed to function as an inhibin B receptor or as an inhibitor of activin type I receptor (ALK4) activity in pituitary gonadotrope cells. If true, loss of IGSF1 should lead to reduced inhibin B action or disinhibition of activin signaling, thereby increasing FSH synthesis. Here, we show that FSH levels and sperm counts are normal in male Igsf1 knockout mice, although testis size is mildly increased. Sperm parameters are also normal in men with IGSF1 deficiency, although their FSH levels may trend higher and their testes are enlarged. Inhibin B retains the ability to suppress FSH synthesis in pituitaries of Igsf1-knockout mice and IGSF1 does not interact with ALK4 or alter activin A/ALK4 stimulation of FSHß (Fshb/FSHB) subunit transcription or expression. In light of these results, it is unlikely that macroorchidism in IGSF1 deficiency derives from alterations in spermatogenesis or inhibin/activin regulation of FSH.

11.
J Clin Res Pediatr Endocrinol ; 13(4): 461-467, 2021 11 25.
Article in English | MEDLINE | ID: mdl-33045800

ABSTRACT

Our objective was to further expand the spectrum of clinical characteristics of the IGSF1 deficiency syndrome in affected males. These characteristic include almost universal congenital central hypothyroidism (CeH) with disharmonious pubertal development (normally timed testicular growth, but delayed rise of serum testosterone), macroorchidism, increased body mass index (BMI), and decreased attentional control. In addition, a subset of patients show prolactin deficiency, transient partial growth hormone deficiency in childhood and increased growth hormone secretion in adulthood. We present a family in which the proband was diagnosed with CeH and low serum prolactin. Severe weight gain started at two years old, with a BMI of 42.3 at 13.9 years. Testicular enlargement (5-6 mL, 3.8-4.3 standard deviation score) started aged three years. A pathogenic variant was found in the IGSF1 gene: c.3411_3412del, p.(Tyr1137*). His brother was referred for short stature at age 13 years and was diagnosed with CeH, normal serum prolactin and IGF-1, and disharmonious puberty. In four male relatives (the proband's brother and three cousins) with the variant (one adult), free thyroxine (fT4) was below the lower limit of the reference range in two, and just above this limit in the other two. Three were overweight or obese, adolescents had disharmonious pubertal development and the adult had profound macroorchidism. In conclusion, male hemizygous carriers of a pathogenic IGSF1 variant can present with fT4 concentration above the lower limit of the reference range while severe early onset obesity or premature testicular growth are part of the phenotypic spectrum.


Subject(s)
Congenital Hypothyroidism , Gonadal Disorders , Immunoglobulins , Membrane Proteins , Obesity , Prolactin/blood , Testis/growth & development , Thyroxine/blood , Adolescent , Congenital Hypothyroidism/blood , Congenital Hypothyroidism/genetics , Gonadal Disorders/blood , Gonadal Disorders/genetics , Humans , Immunoglobulins/deficiency , Immunoglobulins/genetics , Male , Membrane Proteins/deficiency , Membrane Proteins/genetics , Obesity/blood , Obesity/genetics , Obesity, Morbid/blood , Obesity, Morbid/genetics , Pediatric Obesity/blood , Pediatric Obesity/genetics , Pedigree , Syndrome
12.
Ned Tijdschr Geneeskd ; 1642020 04 16.
Article in Dutch | MEDLINE | ID: mdl-32395950

ABSTRACT

A 4-year-old girl presented with an alteration of consciousness and absence of speech after a short period of vomiting, diarrhoea and fever. MRI of the brain revealed a focal lesion in the splenium of the corpus callosum. Rotavirus was detected in the faeces. We concluded that the rotavirus infection had caused mild encephalopathy with a reversible splenial lesion.


Subject(s)
Brain Diseases/diagnosis , Corpus Callosum , Rotavirus Infections , Rotavirus/isolation & purification , Speech Disorders/diagnosis , Unconsciousness/diagnosis , Brain Diseases/physiopathology , Brain Diseases/virology , Child, Preschool , Corpus Callosum/diagnostic imaging , Corpus Callosum/pathology , Diagnosis, Differential , Feces/virology , Female , Humans , Magnetic Resonance Imaging/methods , Rotavirus Infections/complications , Rotavirus Infections/diagnosis , Rotavirus Infections/physiopathology , Speech Disorders/etiology , Unconsciousness/etiology
14.
J Clin Endocrinol Metab ; 105(3)2020 Mar 01.
Article in English | MEDLINE | ID: mdl-31650157

ABSTRACT

CONTEXT: The X-linked immunoglobulin superfamily, member 1 (IGSF1), gene is highly expressed in the hypothalamus and in pituitary cells of the POU1F1 lineage. Human loss-of-function mutations in IGSF1 cause central hypothyroidism, hypoprolactinemia, and macroorchidism. Additionally, most affected adults exhibit higher than average IGF-1 levels and anecdotal reports describe acromegaloid features in older subjects. However, somatotrope function has not yet been formally evaluated in this condition. OBJECTIVE: We aimed to evaluate the role of IGSF1 in human and murine somatotrope function. PATIENTS, DESIGN, AND SETTING: We evaluated 21 adult males harboring hemizygous IGSF1 loss-of-function mutations for features of GH excess, in an academic clinical setting. MAIN OUTCOME MEASURES: We compared biochemical and tissue markers of GH excess in patients and controls, including 24-hour GH profile studies in 7 patients. Parallel studies were undertaken in male Igsf1-deficient mice and wild-type littermates. RESULTS: IGSF1-deficient adult male patients demonstrated acromegaloid facial features with increased head circumference as well as increased finger soft-tissue thickness. Median serum IGF-1 concentrations were elevated, and 24-hour GH profile studies confirmed 2- to 3-fold increased median basal, pulsatile, and total GH secretion. Male Igsf1-deficient mice also demonstrated features of GH excess with increased lean mass, organ size, and skeletal dimensions and elevated mean circulating IGF-1 and pituitary GH levels. CONCLUSIONS: We demonstrate somatotrope neurosecretory hyperfunction in IGSF1-deficient humans and mice. These observations define a hitherto uncharacterized role for IGSF1 in somatotropes and indicate that patients with IGSF1 mutations should be evaluated for long-term consequences of increased GH exposure.


Subject(s)
Immunoglobulins/physiology , Intercellular Signaling Peptides and Proteins/physiology , Membrane Proteins/physiology , Neurosecretion/physiology , Somatotrophs/physiology , Adult , Aged , Aged, 80 and over , Animals , Growth Hormone/biosynthesis , Humans , Immunoglobulins/deficiency , Insulin-Like Growth Factor I/analysis , Intercellular Signaling Peptides and Proteins/deficiency , Male , Membrane Proteins/deficiency , Mice , Middle Aged
15.
Horm Res Paediatr ; 92(6): 372-381, 2019.
Article in English | MEDLINE | ID: mdl-32344414

ABSTRACT

INTRODUCTION: Short stature homeobox-containing gene (SHOX) haploinsufficiency is associated with short stature, Madelung deformity and mesomelia. Current clinical screening tools are based on patients with intragenic variants or deletions. However, recent discoveries showed that deletions of the enhancer elements are quite common. The majority of these patients show less body disproportion and respond better to recombinant human growth hormone treatment. We redefined clinical criteria for genetic analysis to facilitate detection of the full spectrum of SHOX haploinsufficiency. METHODS: We analyzed 51 children with SHOX variants or deletions and 25 children with a deletion in its enhancer region. Data were compared to 277 children referred for suspicion of growth failure without endocrine or genetic pathology. RESULTS: Only half of the patients with an enhancer region deletion fulfilled any of the current screening criteria. We propose new clinical criteria based on sitting height to height ratio >1 SDS or arm span ≥3 cm below height, with a sensitivity of 99%. When these criteria are combined with obligatory short stature, the sensitivity to detect SHOX haploinsufficiency is 68.1%, the specificity 80.6%, and the number needed to screen 21 patients. CONCLUSION: Novel clinical criteria for screening for SHOX haploinsufficiency allow the detection of patients within the full genetic spectrum, that is, intragenic variants and enhancer region deletions.


Subject(s)
Base Sequence , Enhancer Elements, Genetic , Growth Disorders/genetics , Haploinsufficiency , Sequence Deletion , Short Stature Homeobox Protein/genetics , Child , Child, Preschool , Female , Humans , Male , Retrospective Studies
16.
J Endocr Soc ; 2(3): 220-231, 2018 Mar 01.
Article in English | MEDLINE | ID: mdl-29594256

ABSTRACT

Immunoglobulin superfamily, member 1 (IGSF1) is a transmembrane glycoprotein highly expressed in the mammalian pituitary gland. Shortly after its discovery in 1998, the protein was proposed to function as a coreceptor for inhibins (and was even temporarily renamed inhibin binding protein). However, subsequent investigations, both in vitro and in vivo, failed to support a role for IGSF1 in inhibin action. Research on IGSF1 nearly ground to a halt until 2011, when next-generation sequencing identified mutations in the X-linked IGSF1 gene in boys and men with congenital central hypothyroidism. IGSF1 was localized to thyrotrope cells, implicating the protein in pituitary control of the thyroid. Investigations in two Igsf1 knockout mouse models converged to show that IGSF1 deficiency leads to reduced expression of the receptor for thyrotropin-releasing hormone (TRH) and impaired TRH stimulation of thyrotropin secretion, providing a candidate mechanism for the central hypothyroidism observed in patients. Nevertheless, the normal functions of IGSF1 in thyrotropes and other cells remain unresolved. Moreover, IGSF1 mutations are also commonly associated with other clinical phenotypes, including prolactin and growth hormone dysregulation, and macroorchidism. How the loss of IGSF1 produces these characteristics is unknown. Although early studies of IGSF1 ran into roadblocks and blind alleys, armed with the results of detailed clinical investigations, powerful mouse models, and new reagents, the field is now poised to discover IGSF1's function in endocrine tissues, including the pituitary and testes.

17.
PLoS One ; 12(7): e0180731, 2017.
Article in English | MEDLINE | ID: mdl-28686733

ABSTRACT

Mutations in the immunoglobulin superfamily, member 1 gene (IGSF1/Igsf1) cause an X-linked form of central hypothyroidism. The canonical form of IGSF1 is a transmembrane glycoprotein with 12 immunoglobulin (Ig) loops. The protein is co-translationally cleaved into two sub-domains. The carboxyl-terminal domain (CTD), which contains the last 7 Ig loops, is trafficked to the plasma membrane. Most pathogenic mutations in IGSF1 map to the portion of the gene encoding the CTD. IGSF1/Igsf1 encodes a variety of transcripts. A little studied, but abundant splice variant encodes a truncated form of the protein, predicted to contain the first 2 Ig loops of the full-length IGSF1. The protein (hereafter referred to as IGSF1 isoform 2 or IGSF1-2) is likely retained in most individuals with IGSF1 mutations. Here, we characterized basic biochemical properties of the protein as a foray into understanding its potential function. IGSF1-2, like the IGSF1-CTD, is a glycoprotein. In both mouse and rat, the protein is N-glycosylated at a single asparagine residue in the first Ig loop. Contrary to earlier predictions, neither the murine nor rat IGSF1-2 is secreted from heterologous or homologous cells. In addition, neither protein associates with the plasma membrane. Rather, IGSF1-2 appears to be retained in the endoplasmic reticulum. Whether the protein plays intracellular functions or is trafficked through the secretory pathway under certain physiologic or pathophysiologic conditions has yet to be determined.


Subject(s)
Hypothyroidism/genetics , Immunoglobulins/genetics , Membrane Proteins/genetics , Protein Isoforms/genetics , RNA, Messenger/genetics , Animals , Cell Membrane/genetics , Cytoplasm/metabolism , Humans , Hypothyroidism/pathology , Male , Mice , Mutation , RNA Isoforms/genetics , Rats , Testis/metabolism , Testis/pathology
18.
Endocrinology ; 158(4): 815-830, 2017 04 01.
Article in English | MEDLINE | ID: mdl-28324000

ABSTRACT

Loss-of-function mutations in the X-linked immunoglobulin superfamily, member 1 (IGSF1) gene cause central hypothyroidism. IGSF1 is a transmembrane glycoprotein of unknown function expressed in thyrotropin (TSH)-producing thyrotrope cells of the anterior pituitary gland. The protein is cotranslationally cleaved, with only its C-terminal domain (CTD) being trafficked to the plasma membrane. Most intragenic IGSF1 mutations in humans map to the CTD. In this study, we used CRISPR-Cas9 to introduce a loss-of-function mutation into the IGSF1-CTD in mice. The modified allele encodes a truncated protein that fails to traffic to the plasma membrane. Under standard laboratory conditions, Igsf1-deficient males exhibit normal serum TSH levels as well as normal numbers of TSH-expressing thyrotropes. However, pituitary expression of the TSH subunit genes and TSH protein content are reduced, as is expression of the receptor for thyrotropin-releasing hormone (TRH). When challenged with exogenous TRH, Igsf1-deficient males release TSH, but to a significantly lesser extent than do their wild-type littermates. The mice show similarly attenuated TSH secretion when rendered profoundly hypothyroid with a low iodine diet supplemented with propylthiouracil. Collectively, these results indicate that impairments in pituitary TRH receptor expression and/or downstream signaling underlie central hypothyroidism in IGSF1 deficiency syndrome.


Subject(s)
Immunoglobulins/genetics , Membrane Proteins/genetics , Pituitary Gland/metabolism , Receptors, Thyrotropin-Releasing Hormone/metabolism , Thyrotropin-Releasing Hormone/metabolism , Thyrotropin/metabolism , Animals , Immunoglobulins/metabolism , Male , Membrane Proteins/metabolism , Mice , Mice, Knockout , Receptors, Thyrotropin-Releasing Hormone/genetics , Signal Transduction/physiology , Thyrotropin/genetics , Thyrotropin-Releasing Hormone/genetics
19.
J Clin Endocrinol Metab ; 101(12): 4564-4573, 2016 12.
Article in English | MEDLINE | ID: mdl-27603907

ABSTRACT

CONTEXT: Isolated congenital central hypothyroidism (CeH) can result from mutations in TRHR, TSHB, and IGSF1, but its etiology often remains unexplained. We identified a missense mutation in the transducin ß-like protein 1, X-linked (TBL1X) gene in three relatives diagnosed with isolated CeH. TBL1X is part of the thyroid hormone receptor-corepressor complex. OBJECTIVE: The objectives of the study were the identification of TBL1X mutations in patients with unexplained isolated CeH, Sanger sequencing of relatives of affected individuals, and clinical and biochemical characterization; in vitro investigation of functional consequences of mutations; and mRNA expression in, and immunostaining of, human hypothalami and pituitary glands. DESIGN: This was an observational study. SETTING: The study was conducted at university medical centers. PATIENTS: Nineteen individuals with and seven without a mutation participated in the study. MAIN OUTCOME MEASURES: Outcome measures included sequencing results, clinical and biochemical characteristics of mutation carriers, and results of in vitro functional and expression studies. RESULTS: Sanger sequencing yielded five additional mutations. All patients (n = 8; six males) were previously diagnosed with CeH (free T4 [FT4] concentration below the reference interval, normal thyrotropin). Eleven relatives (two males) also carried mutations. One female had CeH, whereas 10 others had low-normal FT4 concentrations. As a group, adult mutation carriers had 20%-25% lower FT4 concentrations than controls. Twelve of 19 evaluated carriers had hearing loss. Mutations are located in the highly conserved WD40-repeat domain of the protein, influencing its expression and thermal stability. TBL1X mRNA and protein are expressed in the human hypothalamus and pituitary. CONCLUSIONS: TBL1X mutations are associated with CeH and hearing loss. FT4 concentrations in mutation carriers vary from low-normal to values compatible with CeH.


Subject(s)
Hearing Loss/genetics , Hypothyroidism/genetics , Pituitary Gland/metabolism , Thyroxine/blood , Transducin/genetics , Adolescent , Adult , Child , Female , Hearing Loss/etiology , Heterozygote , Humans , Hypothalamus/metabolism , Hypothyroidism/blood , Hypothyroidism/complications , Infant , Male , Middle Aged , Mutation , Pedigree , RNA, Messenger/metabolism , Young Adult
20.
Psychoneuroendocrinology ; 72: 80-6, 2016 10.
Article in English | MEDLINE | ID: mdl-27388687

ABSTRACT

In patients with adrenal insufficiency (AI) a higher hydrocortisone intake has been associated with more impairment in quality of life (QoL). Irrespective of age, sex and severity of AI the dosage of hydrocortisone is titrated around 20mg/D in all patients with AI based on physical and mental signs and symptoms. However, until now it is unknown whether these QoL impairments are related to increased systemic cortisol exposure. Measurement of hair cortisol levels (CORThair) can be used to assess chronic systemic cortisol exposure. This study aimed to explore whether QoL in patients with AI is associated with CORThair and daily hydrocortisone intake. We performed a cross-sectional study in 120 patients with AI on stable hydrocortisone replacement, in whom hair samples and QoL data were collected. CORThair were measured with ELISA, and QoL was assessed with validated questionnaires (SF-36, EQ-5D, HADS, MFI-20). Patients reported impairments in 14 of 15 QoL subscales (p<0.001). More impairments in physical aspects of QoL correlated with higher CORThair and higher daily hydrocortisone intake (p<0.05), an effect that was more pronounced in female patients. Regression analyses including both CORThair and hydrocortisone intake revealed a significant negative contribution of higher hydrocortisone intake on physical aspects of QoL (p≤0.046), whereas no significant contribution was found for CORThair. The present study showed that patients with AI report several impairments in QoL which are associated with hydrocortisone intake, and to a lesser extent reflected by chronic systemic cortisol exposure as measured by hair cortisol. This suggests that QoL impairments in patients with AI are not per se the effect of prolonged exposure to elevated systemic cortisol levels.


Subject(s)
Adrenal Insufficiency/drug therapy , Glucocorticoids , Hydrocortisone , Quality of Life , Adult , Aged , Cross-Sectional Studies , Female , Follow-Up Studies , Glucocorticoids/administration & dosage , Glucocorticoids/adverse effects , Glucocorticoids/metabolism , Hair/chemistry , Humans , Hydrocortisone/administration & dosage , Hydrocortisone/adverse effects , Hydrocortisone/metabolism , Male , Middle Aged , Sex Factors
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