Dirk Schnabel

Choreoathetosis, hypothyroidism, and pulmonary alterations due to human NKX2-1 haploinsufficiency.

The occurrence of neurological symptoms and developmental delay in patients affected by congenital hypothyroidism (CH) has been attributed to the lack of thyroid hormone in the developing CNS. Accordingly, after the introduction of neonatal screening programs for CH, which allowed early and adequate treatment, an almost normal outcome for most CH patients could be achieved. However, a few patients did not reach this favorable outcome despite early and adequate treatment. Here we describe five patients with variable degrees of CH who suffered from choreoathetosis, muscular hypotonia, and pulmonary problems, an association of symptoms that had not been described before this study. Since this clinical picture matched the phenotype of mice targeted for deletion of the transcription factor gene Nkx2-1, we investigated the human NKX2-1 gene in these five patients. We found heterozygous loss of function mutations in each of these five patients, e.g., one complete gene deletion, one missense mutation (G2626T), and three nonsense mutations (2595insGG, C2519A, C1302A). Therefore, the unfavorable outcome in patients with CH, especially those with choreoathetosis and pulmonary symptoms, can be explained by mutations in the NKX2-1 gene rather than by hypothyroidism. Moreover, the association of symptoms in the patients with NKX2-1 mutations points to an important role of human NKX2-1 in the development and function of thyroid, basal ganglia, and lung, as already described for rodents.

Phenotypic classification of male pseudohermaphroditism due to steroid 5α‐reductase 2 deficiency

Conversion of testosterone (T) to dihydrotestosterone (DHT) in genital tissue is catalysed by the enzyme 5 alpha-reductase 2, which is encoded by the SRD5A2 gene. The potent androgen DHT is required for full masculinization of the external genitalia. Mutations of the SRD5A2 gene inhibit enzyme activity, diminish DHT formation, and hence cause masculinization defects of varying degree. The classical syndrome, formerly described as pseudovaginal perineoscrotal hypospadias, is characterized by a predominantly female phenotype at birth and significant virilization without gynecomastia at puberty. We investigated nine patients with steroid 5 alpha-reductase 2 deficiency (SRD). Phenotypes, which were classified according to the severity of the masculinization defect, varied between completely female (SRD type 5), predominantly female (SRD type 4), ambiguous (SRD type 3), predominantly male with micropenis and hypospadias (SRD type 2), and completely male without overt signs of undermasculinization (SRD type 1). T/DHT-ratios were highly increased ( > 50) in the classical syndrome (SRD type 5), but variable in the less severe affected patients (SRD types 1-4) (14-35). Mutations in the SRD5A2 gene had been characterized using PCR-SSCP analysis and direct DNA sequencing. A small deletion was encountered in two patients, while all other patients had single base mutations which result in amino acid substitutions. We conclude that phenotypes may vary widely in patients with SRD5A2 gene mutations spanning the whole range from completely female to normal male without distinctive clinical signs of the disease. Hence, steroid 5 alpha-reductase deficiency should be considered not only in sex reversed patients with female or ambiguous phenotypes, but also in those with mild symptoms of undermasculinization as encountered in patients with hypospadias and/or micropenis. A classification based on the severity of the masculinization defect may be used for correlation of phenotypes with enzyme activities and genotypes, and for comparisons of phenotypes between different patients as the basis for clinical decisions to be made in patients with pseudohermaphroditism due to steroid 5 alpha-reductase 2 deficiency.

Five novel mutations in steroidogenic factor 1 (SF1, NR5A1) in 46,XY patients with severe underandrogenization but without adrenal insufficiency

Steroidogenic factor 1 (SF1, NR5A1) is a nuclear receptor that regulates multiple genes involved in adrenal and gonadal development, steroidogenesis, and the reproductive axis. Human mutations in SF1 were initially found in two 46,XY female patients with severe gonadal dysgenesis and primary adrenal failure. However, more recent case reports have suggested that heterozygous mutations in SF1 may also be found in patients with 46,XY partial gonadal dysgenesis and underandrogenization but normal adrenal function. We have analyzed the gene encoding SF1 (NR5A1) in a cohort of 27 patients with 46,XY disorders of sex development (DSD) from the German network of DSD. Heterozygous SF1 mutations were found in 5 out of 27 (18.5%) of cases. Four patients with SF1 mutations presented with the similar phenotype of mild gonadal dysgenesis, severe underandrogenization, and absent Müllerian structures. Of these, two patients harbored missense mutations within the DNA‐binding region of SF1 (p.C33S, p.R84H), one patient had a nonsense mutation (p.Y138X) and one patient had a frameshift mutation (c.1277dupT) predicted to disrupt RNA stability or protein function. One additional patient ([c.424_427dupCCCA]+[p.G146A]) displayed a more marked phenotype of severe gonadal dysgenesis, normal female external genitalia, and Müllerian structures. Functional studies of the missense mutants (p.C33S, p.R84H) and of one nonsense mutant (p.Y138X) revealed impaired transcriptional activation of SF1‐responsive target genes. To date, adrenal insufficiency has not occurred in any of the patients. Thus, SF1 mutations are a relatively frequent cause of 46,XY DSD in humans. Hum Mutat 29(1), 59–64, 2008.

Molecular Pathogenesis of Neonatal Hypothyroidism

In patients with congenital hypothyroidism (CH), the autosomal recessive inheritance of mutations of thyroid peroxidase, thyroglobulin and the NIS and pendrin genes encoding for sodium iodide transporters has been identified. CH due to thyroid dysgenesis was considered to be a sporadic disease, but recently, inheritable defects of thyroid development have been described. The autosomal recessive inheritance of mutations of the thyroid-stimulating hormone receptor gene was recognized in patients with CH and thyroid hypoplasia, while autosomal dominant mutations of the Pax-8 gene were described in patients with thyroid dysgenesis. In addition, analysis of mutations of the β-thyrotropin gene has resulted in a new understanding of the pathogenesis of central CH. Molecular genetic studies in patients with CH detected by newborn screening will provide the information necessary for genetic counselling and may help to explain the less favourable outcome present in 5–10% of the patients.

The use of L-T4 as Liquid solution improves the practicability and individualized dosage in newborns and infants with congenital hypothyroidism

UNLABELLEDnDosage recommendations for the initial therapy of congenital hypothyroidism (CH) in newborns vary between 8 microg/kg/d and 10-15 microg/kg/d.nnnAIMnTo evaluate the practicability of LT4 in liquid form and to define the initial dosage for optimal treatment.nnnMETHODSnLiquid LT4 solution was administered to 28 consecutive newborns with primary CH. We measured TSH, T3, T4, free T3 and free T4 before therapy and during follow-up up to 2 years. After 2 years a standardized developmental test (Griffith) was performed.nnnRESULTSnThe median dosage at start of therapy was 12.3 microg LT4/kg/d and decreased to about 5 microg LT4/kg/d after 9 months. The median time of normalization of TSH (< or =6 mU/l) was 2 weeks. In 21 patients, who received a median starting dosage of 12.7 microg LT4/kg (range 9.8-17.1 microg/kg), TSH levels normalized within a median of 1 week. Seven patients receiving only 10.1 microg LT4/kg normalized their TSH only after a median of 2 months.nnnCONCLUSIONSnNewborns with CH should normalize their TSH within 1-2 weeks. The initial dose necessary to normalize TSH is not lower when a liquid solution is used. The higher dose used in tablets is not due to inefficient absorption, but rather reflects the increased demand for thyroid hormone in the first weeks of life.

Ergebnisse des Neugeborenenscreenings zur Früherkennung des Adrenogenitalen Syndroms in Berlin (1992–1999)

ZusammenfassungHintergrund. In Berlin wurde 1992 die Bestimmung des 17-Hydroxyprogesterons (17-OHP) im Filterpapier als Neugeborenenscreening zur Früherkennung des Adrenogenitalen Syndroms (AGS) eingeführt.nn Diagnose. Seither wurden nahezu 250.000 Neugeborene untersucht, und bei 26 Kindern wurde die Diagnose eines klassischen AGS (21-Hydroxylase-Mangel) gestellt und durch spezifische Steroiduntersuchungen im Serum und die molekulargenetische Diagnostik gesichert. Dies entspricht einer Häufigkeit von 1:9594 Neugeborenen, die den Erfahrungen anderer weltweit durchgeführter Screeningprogramme entspricht und doppelt so hoch wie die Häufigkeit aufgrund klinischer Diagnose ist. Es waren 14 Mädchen und 12 Jungen betroffen, wobei alle Jungen und 8 Mädchen ein AGS mit Salzverlust (77% aller Patienten) aufwiesen. Die Diagnose wurde zwischen dem 2. und 10. Lebenstag (im Mittel 6. Lebenstag) gestellt, und in der Regel wurde bereits am nächsten Tag mit der Substitutionstherapie begonnen. So konnte in allen Fällen eine Stoffwechselkrise vermieden werden. Bei nur 7 der 14 Mädchen bestand der klinische Verdacht aufgrund eines intersexuellen Genitales, sodass bei allen Jungen und der Hälfte der Mädchen die Diagnose allein durch das Screening gestellt wurde. Durch die Anwendung gestationsaltersabhängiger Perzentilen der 17-OHP-Spiegel gelang es, die Recallrate bei Frühgeborenen gering zu halten (0,6%).nn Resümee. Das so durchgeführte Screening erwies sich im Sinn der Kosten-Nutzen-Analyse als geeignet, die Diagnose und Therapie des AGS im Sinn der Qualitätssicherung zu verbessern.AbstractBackground. In 1992 in Berlin a screening for congenital adrenal hyperplasia (CAH) was introduced.nn Diagnosis. Since then nearly 250 000 newborns were screened and 26 newborns with classical CAH due to 21-hydroxylase deficiency were detected. The diagnosis was ascertained by specific determination of serum 17-OHP and molecular genetic diagnosis. The incidence was 1: 9594 newborns, which is comparable to the incidence reported by other screening programs world-wide and double the incidence established by clinical diagnosis. 14 female and 12 male patients were detected, with 12 male and 8 females presenting with the salt-wasting form (77% of all patients). The diagnosis was made between the second and 10th day of life and therapy was started usually on the next day. A metabolic crisis was prevented in all cases. Only in 7 of the 14 girls there was a suspicion of CAH because of an intersexual development of the external genitalia. Thus, in all boys and in 50% of the girls the diagnosis was made by screening. Using gestational age adjusted percentiles of 17-OHP-concentrations the recall rate in preterms was kept low with an overall recall rate of 0.6%.nn Conclusion. Using the described method and procedure newborn screening for CAH proved to be cost-effective in improving the diagnosis and treatment of CAH.

Effects of growth hormone treatment on adult height in severely short children with X-linked hypophosphatemic rickets

BackgroundWe recently showed that a 3-year growth hormone (GH) treatment improves linear growth in severely short children with X-linked hypophosphatemic rickets (XLH). It is unknown if GH therapy increases adult height in XLH patients.MethodsWe carried out a follow-up analysis of a randomized controlled open-label GH study in short prepubertal children with XLH on phosphate and active vitamin D treatment. The changes in SD scores (SDS) of height, sitting height, leg and arm length, and sitting height index (i.e., the ratio between sitting height and height) were analyzed in 11 out of 16 patients followed-up until adult height.ResultsAt baseline, XLH patients showed disproportionately short stature with reduced standardized height (−3.2xa0±xa00.6), sitting height (−1.7xa0±xa00.6), leg (−3.7xa0±xa00.7) and arm (−2.5xa0±xa00.8) length, and markedly elevated sitting height index (3.3xa0±xa00.6; each pxa0<xa00.01 versus healthy children). In GH-treated patients, adult height, sitting height, leg length, and arm length exceeded baseline values by 0.7 SDS, 1.7 SDS, 0.7 SDS, and 1.2 SDS respectively, although this was only significant for sitting height. In controls, no significant changes in linear body dimensions were noted. Adult height did not statistically differ between groups (−2.4xa0±xa00.7 vs −3.3xa0±xa01.2, pxa0=xa00.082). GH did not exaggerate body disproportion.ConclusionsGrowth hormone treatment did not significantly increase adult height in this group of short children with XLH, which may be at least partly due to the small number of patients included in our study.

A new multi-system disorder caused by the Gαs mutation p.F376V.

CONTEXTnThe α subunit of the stimulatory G protein (Gαs) links numerous receptors to adenylyl cyclase. Gαs, encoded by GNAS, is expressed predominantly from the maternal allele in certain tissues. Thus, maternal heterozygous loss-of-function mutations cause hormonal resistance, as in pseudohypoparathyroidism type Ia, whereas somatic gain-of-function mutations cause hormone-independent endocrine stimulation, as in McCune-Albright syndrome.nnnOBJECTIVEnWe report two unrelated boys presenting with a new combination of clinical findings that suggest both gain and loss of Gαs function.nnnDESIGN AND SETTINGnClinical features were studied and sequencing of GNAS was performed. Signaling capacities of wild-type and mutant Gαs were determined in the presence of different G protein-coupled receptors (GPCRs) under basal and agonist-stimulated conditions.nnnRESULTSnBoth unrelated patients presented with unexplained hyponatremia in infancy, followed by severe early onset gonadotrophin-independent precocious puberty and skeletal abnormalities. An identical heterozygous de novo variant (c.1136T>G; p.F376V) was found on the maternal GNAS allele in both patients; this resulted in a clinical phenotype that differed from known Gαs-related diseases and suggested gain of function at the vasopressin 2 receptor (V2R) and lutropin/choriogonadotropin receptor (LHCGR), yet increased serum PTH concentrations indicative of impaired proximal tubular PTH1 receptor (PTH1R) function. In vitro studies demonstrated that Gαs-F376V enhanced ligand-independent signaling at the PTH1R, LHCGR, and V2R and, at the same time, blunted ligand-dependent responses. Structural homology modeling suggested mutation-induced modifications at the C-terminal α5 helix of Gαs that are relevant for interaction with GPCRs and signal transduction.nnnCONCLUSIONSnThe Gαs p.F376V mutation causes a previously unrecognized multisystem disorder.

Increased Transactivation Associated with SOX3 Polyalanine Tract Deletion in a Patient with Hypopituitarism

This article appears in The Journal of Clinical Endocrinology & Metabolism, published February 2, 2011, 10.1210/jc.2010-1239