An activating mutation of the thyrotropin receptor gene in hereditary non-autoimmune hyperthyroidism

The thyroid stimulating hormone (TSH) receptor gene displays a diverse spectrum of activating and inactivating mutations. We report a germline activating mutation M463V of the TSH receptor gene in two siblings with hereditary non-autoimmune hyperthyroidism. The onset of disease in the affected members of the pedigree occurred during childhood or adolescence. The significance of diagnosing activating TSHR mutations lies in therapeutic management and genetic counseling; thyroid ablation is advocated as first line treatment.     

Autoimmune thyroid disease in Libyan children and young adults with type 1 diabetes mellitus

Diabetes mellitus is a common autoimmune endocrine disorder associated with organ-specific autoantibodies which are frequently detected at the time of diagnosis. Some of these antibodies are specific to the pancreas (GAD, IA2, ICA) while others are related to different autoimmune diseases. Aim of the study: To define the prevalence of thyroid autoimmune disease in Libyan patients with type 1 diabetes mellitus (T1DM) since no similar studies have been performed in Libya. Materials and methods: Blood samples were collected from 218 patients with T1DM who are followed by the Pediatric Department, Tripoli Medical Center, Libya. All sera were analyzed in Italy (Laboratory of Immunopathology and Allergy, Udine). The patients were composed of 123 females (56.4%) and 95 males (43.6%), mean age 12.2 ± 4.6 years (range 2.1–24.5 years), mean duration of diabetes 4.7 ± 4.0 years (range 0.1–17.5 years). Sera were tested for anti-thyroperoxidase (TPO) and anti-thyroglobulin antibodies (TG). TSH and FT4 concentrations were measured in all subjects. GAD, IA-2 was also measured. Results: Of the diabetic children, 23.4% were positive for anti-microsomal peroxidase antibodies (TPO-Ab) and 7.8% for antithyroglobulin antibodies (TG-Ab); whereas 6.9% of the patients were positive for both TPO-Ab and TG-Ab. Of the T1DM patients who were positive for TPO-Ab, 66.6% were females. The majority (57%) of the patients who were positive for TPO had diabetes for longer than 5 years. Five patients (2.3%) had evidence of subclinical hypothyroidism whereas two patients (0.9%) had overt hypothyroidism. Two patients had subclinical hyperthyroidism and two (0.9%) had overt hyperthyroidism. Interestingly, 16.2% of patients were positive for both thyroid and pancreatic antibodies. Conclusions: The prevalence of autoimmune thyroid disease in type 1 diabetic patients is higher than in the general population. A routine screening strategy should be implemented with the determination of anti-thyroid antibodies and TSH in type 1 diabetic patients, particularly in girls, and in patients with diabetes of more than 5 years duration. Patients who have positive TPO antibodies may need the assessment of thyroid function at shorter intervals.     

Autosomal-dominant non-autoimmune hyperthyroidism presenting with neuromuscular symptoms

AIM: Neuromuscular presentations are common in thyroid disease, although the mechanism is unclear. In the present study, we investigated the pathogenesis in a boy with autosomal-dominant hyperthyroidism presenting with neuromuscular symptoms. METHODS: The TSHr gene was investigated by direct sequencing. Functional properties of the mutant TSHr were investigated during transient expression in COS-7 cells. Family members were investigated by clinical and biochemical examinations. RESULTS: Sequence analysis revealed a previously reported heterozygous missense mutation Glycine 431 for Serine in the first transmembrane segment, leading to an increased specific constitutive activity. Three additional affected family members carried the same mutation. There was no indication of autoimmune disorder. All symptoms disappeared upon treatment with thacapzol and L-thyroxine and subsequent subtotal thyroidectomy. CONCLUSION: The data imply that neuromuscular symptoms can be caused by excessive thyroid hormone levels rather than by autoimmunity.     

B cell cytopenia in two brothers with hyper-IgD and periodic fever syndrome

We report on two brothers with hyperimmunoglobulinemia D (patient 1: serum immunoglobulin D [IgD] concentration initially 61 IU/ml, later on 340 IU/ml; patient 2: serum IgD concentration 144 IU/ml; normal <100 IU/ml, 97th centile) and periodic fever syndrome (HIDS). Both are compound heterozygous for the mevalonate kinase (MVK) mutations V377I and I268T. They developed significant B cell cytopenia (7%, 129/μl and 11%, 132/μl, respectively; normal ranges 12–22%, 300–500/μl) with hypogammaglobulinemia (IgG 5.48 g/l and IgG 5.22 g/l, respectively; normal range IgG 6–13 g/l). Furthermore, the clinical spectrum shows an interesting atypical autoinflammatory symptomatology. The therapy consisted of prednisone, azathioprine, and intravenous immunoglobulins (IVIG), which results in reduced incidence and severity of febrile attacks. Conclusion: The pathogenesis and clinical presentation of HIDS is still not fully understood and show a great variability. To our knowledge, severe B cell cytopenia in children with HIDS has not been reported before. Furthermore, the therapy of febrile episodes is still performed on an individual basis in affected patients.     

Prevalence of germline mutations in the TSH receptor gene as a cause of juvenile thyrotoxicosis

Aim: To ascertain the prevalence of germline mutations in the TSH receptor gene as a cause of juvenile thyrotoxicosis (JT) in non-autoimmune patients. TSH receptor gene mutations are not seen in autoimmune-active patients. Methods: In a nationwide study on JT, 123 patients were re-examined 10 y (range 4 to 21 y) after diagnosis. Two patients with toxic adenoma were excluded. In 25 patients, no TPO, TG or TSH-R antibodies were found. In 17 patients, DNA material was available for TSH receptor gene analysis. The entire TSH receptor gene was sequenced in five patients. TSH receptor “hot spots” for mutations in exon 9 and 10 were sequenced in the remaining 12 patients. Results: A TSH receptor gene germline mutation was identified in only one patient of a total number of 121 patients with JT, of which 17 patients were presumed to have non-autoimmune JT by the lack of thyroid autoantibodies.

Conclusion: In Denmark the prevalence of germline mutations in the TSH receptor gene is one in 121 patients with JT (0.8%; 95% CI: 0.02-4.6%) and one in 17 patients with presumed non-autoimmune JT (6%; 95% CI: 5.88% (0.15-28.69)).     

Pathology of the TSH receptor

Gain of function and loss of function mutations of the TSH receptor have been implicated in the pathogenesis of various thyroid diseases. Gain of function mutations, when somatic, are the first cause of autonomous nodules; when germline, they are responsible for hereditary non-autoimmune toxic thyroid hyperplasia and for some cases of sporadic congenital hyperthyroidism. A subset of mutations modifying the receptor selectivity have recently been found to be involved in the pathogenesis of familial gestational hyperthyroidism. These mutations are of great interest for understanding the mechanism of receptor activation. Loss of function mutations of the TSH receptor are responsible for different phenotypes ranging from asymptomatic resistance to TSH to overt congenital hypothyroidism.     

Alterations of neonatal thyroid function

Grüters A, Krude H, Biebermann H, Liesenkötter KP, Schöneberg T, Gudermann T. Alterations of neonatal thyroid function. Acta Pædiatr 1999; Suppl 428: 17–22. Stockholm. ISSN 0803–5326
Recent progress has been made in understanding the pathogenesis of neonatal thyroid disorders. Autosomal recessive inheritance of mutations of the thyroid peroxidase and thyroglobulin genes has been described in some patients with congenital hypothyroidism (CH) and a family history of CH. Autosomal recessive inheritance of mutations of the thyrotrophin (TSH) receptor gene has also been reported in patients with CH and thyroid hypoplasia, and autosomal dominant mutations of the PAX8 gene have been described in patients with different forms of thyroid dysgenesis. These discoveries are important for patients with CH diagnosed by neonatal screening, as these patients will have normal fertility. The molecular genetic analysis of mutations of the TSH gene in patients with familial and sporadic cases of isolated central CH, who are missed by TSH screening programmes, now enables rapid diagnosis and appropriate therapy in the neonate. In newborn infants with severe non-autoimmune hyperthyroidism, autosomal dominant gain-of-function mutations in the TSH receptor gene have been demonstrated. In these patients, molecular genetic studies are extremely helpful in therapeutic decision making, as early thyroid ablation is the only effective treatment that avoids the sequelae of long-term hyperthyroidism. Molecular genetic studies are therefore useful in the diagnostic work-up of neonatal thyroid alterations. □ Congenital hypothyroidism, molecular pathogenesis, neonatal hyperthyroidism     

Thyroid dysfunction in antiretroviral treated children

BACKGROUND: A high rate of thyroid disorders has been described in HIV-infected adults treated with highly active antiretroviral therapy (HAART), but data on children are lacking. We aimed to assess thyroid function in pediatric patients. METHODS: Fifty-two HIV-infected children receiving HAART were assessed for signs of thyroid dysfunction and serum concentrations of thyrotropin (TSH), free thyroxin (FT4), free triiodothyronine (FT3), thyroglobulin (TG), reverse triiodothyronine (rT3), anti-TG and antimicrosomal (anti-TSM) antibodies. RESULTS: Eighteen (35%) children showed thyroid abnormalities: isolated low FT4 value in 16; subclinical hypothyroidism in 1; and symptomatic hypothyroidism in 1.Children with low FT4 values as compared with the 34 children without thyroid dysfunction were similar for stage of disease, number of patients with undetectable HIV-RNA, FT3, TSH, TG, rT3, anti-TSM and anti-TG values, whereas they had shorter duration of HAART exposure (P = 0.019) and lower CD4 cell percentage (P = 0.035). The thyrotropin-releasing hormone (TRH) test was normal in all children with low FT4 values. Among children with low FT4, FT4 concentrations correlated positively with CD4 cell percentage (P < 0.05) and duration of HAART exposure (P < 0.05).The case with subclinical hypothyroidism had high basal TSH (7.3 microunits/ml), normal TSH response to TRH test and normal FT4, FT3, TG, rT3, anti-TG and anti-TSM antibodies.The case with symptomatic hypothyroidism had low FT4 (6.6 pg/ml) and high TSH (44 microunits/ml), TG (55 ng/ml), anti-TG (666 IU/ml) and anti-TSM (123 IU/ml). CONCLUSION: Thyroid abnormalities occur frequently in HAART-treated children even in the absence of clinical symptoms. These data suggest a need of regular thyroid function monitoring.     

Sporadic congenital nonautoimmune hyperthyroidism caused by P639S mutation in thyrotropin receptor gene

Germline mutations of thyrotropin receptor (TSHR) gene determining a constitutive activation of the receptor were identified as a molecular cause of familial or sporadic congenital nonautoimmune hyperthyroidism (OMIM: 609152) (Nat Genet 7:396-401, 1994; N Engl J Med 332:150-154, 1995; Acta Endocrinol (Copenh) 100:512-518, 1982). We report the case of an Italian child subjected to the first clinical investigation at 24?months for an increased growth velocity; biochemical investigation showed high FT4 and FT3 serum values and undetectable thyrotropin in the absence of anti-thyroid antibodies; the thyroid gland was normal at ultrasound examination. Treatment with methimazole was started at the age of 30?months when her growth velocity was high and the bone age was advanced. DNA was extracted from her parents', brother's, and the patient's blood. Exons 9 and 10 of the TSHR gene were amplified by polymerase chain reaction and subjected to direct sequencing. In proband, a heterozygous substitution of cytosine to thymine determining a proline to serine change at position 639 (P639S) of the TSHR was detected while the parents and brothers of the propositus, all euthyroid, showed only the wild-type sequence of the TSHR gene. This mutation was previously described as somatic in patients affected by hyperfunctioning thyroid nodules and as germline in a single Chinese family affected by thyrotoxicosis and mitral valve prolapse. This constitutively activating mutation is able to activate both the cyclic AMP and the inositol phosphate metabolic pathways when expressed in a heterologous system. In conclusion, we describe the first case of sporadic congenital nonautoimmune hyperthyroidism caused by de novo germinal P639S mutation of TSHR.     

A mutation in thyroid hormone receptor beta causing "resistance to thyroid hormone" in a neonate

Resistance to thyroid hormone (RTH) is an inherited syndrome characterized by reduced tissue responsiveness to thyroid hormones. The main defects are due to mutations in thyroid hormone receptor beta (TRbeta). A male, term neonate was admitted because of indirect hyperbilirubinemia and polycythemia. Physical examination revealed ophtalmopathy. High serum T? with unsupressed thyroid stimulating hormone (TSH) levels suggested RTH. In this presented case, A317T mutation was detected on exon 9 of the TRb-1 gene and precise diagnosis had been confirmed with genetic testing. In neonates and infants exhibiting hypo or hyperthyroidism features with increased circulating levels of thyroid hormones with a normal or increased serum TSH concentration should raise the suspicion of RTH.     

Subclinical hyperthyroidism due to a thyrotropin receptor (TSHR) gene mutation (S505R)

AIM: To identify the molecular defect by which non-autoimmune subclinical hyperthyroidism was caused in a 6-mo-old infant who presented with weight loss. METHODS: Congenital non-autoimmune hyperthyroidism is caused by activating germline mutations in the thyrotropin receptor (TSHR) gene. Therefore, the TSHR gene was sequenced directly from the patient's genomic DNA. RESULTS: Molecular analysis revealed a heterozygous point mutation (S505R) in the TSHR gene as the underlying defect. CONCLUSION: A constitutively activating mutation in the TSHR gene has to be considered not only in patients with severe congenital non-autoimmune hyperthyroidism, but also in children with subclinical non-autoimmune hyperthyroidism.     

A Case with Hyperthyroidism Who Had Been Treated with Thyroid Hormone Because of Congenital Hypothyroidism

We encountered a case with hyperthyroidism at the age of 14 who had been diagnosed with congenital hypothyroidism (CH) and had received thyroid hormone replacement therapy. At the age of 16 d, the patient was referred to our hospital because of positive results at neonatal screening for CH. Serum level of TSH was 91.0 μU/ml and serum level of T4 was 6.9 μg/dl. The patient was diagnosed as having hypothyroidism, and hormone replacement therapy was started. Thereafter the dosage of thyroid hormone was adjusted and increased gradually as he grew to a maximum dose of 110 μg/day at the age of 11. Until the age of 13, the patient’s serum levels of TSH were within the normal range; then, at the age of 13 yr and 4 mo, his serum level of TSH dropped to a level below the detectable range. The dosage of administered thyroid hormone was tapered off and eventually eliminated at the age of 14. A thyroid scan and a radioactive iodine uptake test demonstrated a diffuse goiter with homogeneous uptake of radioactive iodine; the uptake rate was 60% at 24 h, and the serum level of TSH receptor antibody (TRAb) was 62.5% at that time. Administration of an antithyroid drug was started after confirmation that our patient had developed hyperthyroidism. There have been no case reports similar to our case.     

Serum cytokine profile in reflux nephropathy

Cytokines are small regulatory peptides with diverse functions. They regulate the immune system and modulate the inflammatory response, both of which are implicated in vesico-ureteric reflux (VUR) and associated reflux nephropathy (RN). The cytokine profile in VUR and RN has yet to be fully investigated. Blood was obtained from three subject groups immediately after induction of anaesthesia: group A [subjects with VUR and established RN, (N=9)]; group B [VUR alone but no associated RN, (N=6)]; and group C [age- and sex-matched controls with no history of urinary sepsis, (N=14)]. Serum cytokine levels of tumour-necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), soluble TNF receptor-1 (sTNF-R1), and interleukin-8 (IL-8) were measured using standard ELISA technique. Serum levels of IL-6 were higher in group A subjects (1.798–4.638 pg/ml, median 3.253 pg/ml) than controls (1.531–2.078 pg/ml, median 1.798 pg/ml). There was no significant difference in levels in group B subjects (1.498–3.048 pg/ml, median 1.948 pg/ml) and controls. These same relationships were observed for levels of TNF-α (group A: 8.501–14.471 pg/ml, median 13.483 pg/ml; group B: 7.088–10.650 pg/ml, median 8.886 pg/ml; group C: 6.746–13.344 pg/ml, median 7.671 pg/ml) and sTNF-R1 (group A: 690.34–5780.74 pg/ml, median 1197.38 pg/ml; group B: 366.65–1401.62 pg/ml, median 592.82 pg/ml; C: 313.49–636.33 pg/ml, median 504.17 pg/ml). IL-8 was not significantly elevated in any of the study groups (A or B) compared with control group C (group A: 27.08–56.38 pg/ml, median 31.35 pg/ml; group B: 29.90–35.87 pg/ml, median 31.35 pg/ml; group C: 25.05–30.22 pg/ml, median 29.90 pg/ml). These results suggest there may be an immunological basis to RN. Accepted: 21 December 1998     

Alterations of neonatal thyroid function

Recent progress has been made in understanding the pathogenesis of neonatal thyroid disorders. Autosomal recessive inheritance of mutations of the thyroid peroxidase and thyroglobulin genes has been described in some patients with congenital hypothyroidism (CH) and a family history of CH. Autosomal recessive inheritance of mutations of the thyrotrophin (TSH) receptor gene has also been reported in patients with CH and thyroid hypoplasia, and autosomal dominant mutations of the PAX8 gene have been described in patients with different forms of thyroid dysgenesis. These discoveries are important for patients with CH diagnosed by neonatal screening, as these patients will have normal fertility. The molecular genetic analysis of mutations of the TSH gene in patients with familial and sporadic cases of isolated central CH, who are missed by TSH screening programmes, now enables rapid diagnosis and appropriate therapy in the neonate. In newborn infants with severe non-autoimmune hyperthyroidism, autosomal dominant gain-of-function mutations in the TSH receptor gene have been demonstrated. In these patients, molecular genetic studies are extremely helpful in therapeutic decision making, as early thyroid ablation is the only effective treatment that avoids the sequelae of long-term hyperthyroidism. Molecular genetic studies are therefore useful in the diagnostic work-up of neonatal thyroid alterations.     

Hyperthyroidism in children

This study was done to characterize the clinical features, laboratory parameters and response to therapy and outcome of childhood hyperthyroidism. The evaluation included history, examination, laboratory investigations: serum T₃ T₄, TSH free T₃, free T₄ by RIA or immunochemiluminescence (IC), antithyroid antibodies by standard techniques, bone age (BA) by Greulich and Pyle’s method, clinical and laboratory response to treatment, and follow-up of 15 children with hyperthyroidism seen in past eight years. Age of onset, presentation, nature and duration of symptoms, family history, anthropometry and signs of hyperthyroidism were recorded. There were 10 girls and 5 boys (2∶1). Three families had a history of thyroid disorders. Mean ages of onset and presentation were 8.25±3.4 and 9.27±3.2 years respectively. Clinical features included weight loss, heat intolerance and sweating, diarrhoea, behavioral problems, ophthalmopathy and tachycardia. BA was advanced. serum T₃ (mean=4.29±1.77 ng/mL), T₄ (18.75±5.64 μg/dL), FT₃ (7.11±4.58 pg/mL) and FT₄ (2.93±0.29 ng/mL) were markedly elevated. TSH was suppressed. Anti-microsomal antibodies (AMA) and anti-thyroglobulin antibodies (ATG) were positive in five. They were started on standard treatment with carbimazole 0.5–0.7 mg kg¹. Clinical and biochemical euthyroidism was achieved within 2.5 to 6 months in all, after which the drug was tapered, however, they required treatment for 2 years to 7.5 years. Four children were retreated for relapse and are now euthyroid and off treatment. Childhood hyperthyroidism requires long term treatment and careful monitoring. This study shows a remission rate of 67%.     

A thyroxine dosage of 8 μg/kg per day is appropriate for the initial treatment of the majority of infants with congenital hypothyroidism

 The adequate l-thyroxine dosage for the initial treatment of infants with congenital hypothyroidism is a subject of controversy. Some recommend higher dosages (> 10 μg/kg/day) to ensure adequate levels, while others advocate lower dosages to permit normalisation of thyroid status. The aim of this study was to evaluate the␣results of a treatment strategy using an initial dosage of 7.5–8.0 μg/kg per day, TSH measurements being␣taken at 15 and 30 days of treatment. Fifty one newborns infants with primary congenital hypothyroidism␣detected by neonatal screening were treated with the same therapeutic strategy. A mean l-thyroxine dosage of 7.9 μg/kg per day at the onset of treatment and 6.6 μg/kg/d at 2 months, normalised the FT₄ and FT₃ levels at 15 days in 100% and TSH levels at 2 months in 90% of cases. Many patients showed elevated levels of FT₄ and a systematic higher initial dosage could expose many infants to a dangerous hyperthyroidism. Patients with abnormal TSH levels at 2 months already had higher TSH levels in the first 8 weeks of life and, despite higher l-thyroxine dosage, also exhibited lower FT₄ and FT₃ levels. These patients who needed an early increase in dosage had already shown a more profound ante and neonatal hypothyroidism. This subgroup of patients require a higher dosage of thyroxine and early assessment of FT₄, FT₃ and TSH levels are required for optimum dosage choice. Conclusion Even though a subgroup of patients may require a higher dosage of l-thyroxine, an initial␣dosage of 7.5–8.0 μg/kg per day, with an early assessment of␣FT₄, FT₃, and TSH levels, is adequate for the treatment of the majority of infants with congenital hypothyroidism. Received: 17 August 1995 / Accepted 10 June 1996     

A case of hypomagnesemia with secondary hypocalcemia caused by Trpm6 gene mutation

An offspring of marriage between two first cousins presented with atonic seizures developed on the 20^th day of life. The physical examination of the case was normal. In laboratory results, Ca+² level was 5,7 mg/dl, Mg+²: 0,4 mg/dl (1,3–2,1), PTH: 28,4 pg/ml (12–92), and P-: 4,5 mg/dl. The case was diagnosed as hypomagnesemia with secondary hypocalcemia (HSH) and TRPM6 gene mutation analysis revealed a homozygote mutation of E157X.     

Phaeochromocytoma associated with a de novo VHL mutation as form fruste of von Hippel-Lindau disease

 Phaeochromocytomas usually occur sporadically but may be associated with dominant inherited cancer syndromes such as multiple endocrine neoplasia type 2 (MEN 2), von Hippel-Lindau disease (VHL) and type 1 neurofibromatosis. We report on a boy presenting at age 8 years with an isolated benign phaeochromocytoma of the left adrenal. Three years later a second adrenal phaeochromocytoma was diagnosed on the right side and removed. His family history was negative. Genetic analysis did not show a mutation in the MEN 2 susceptible proto-oncogene rearranged during transfection; however, we found a germline missense mutation in the VHL gene (nucleotide 695 G to A transversion) which has been described only twice before in the literature. Both parents had normal (wild type) VHL copies indicating that our patient had a de novo germline VHL mutation. Careful clinical evaluation of the patient at 18 years did not reveal any other manifestations of VHL disease. Conclusion Carriers of von Hippel-Lindau germline mutations can present with a form fruste of von Hippel-Lindau disease presenting initially with unilateral phaeo-chromocytoma and therefore mutation analysis should be carried out. Received: 21 June 2000 and in revised form: 18 February 2001 / Accepted: 20 February 2001     

A further case of renal tubular dysgenesis surviving the neonatal period

Renal tubular dysgenesis is a critical disorder characterized by the Potter phenotype and severe hypotension in the early neonatal period. We herein report a 3-year-old female with renal tubular dysgenesis. Endocrinological studies showed a high plasma renin activity (over 49.2 ng/ml/h; normal range 2.0–15.2), high active renin concentration (1,823.5 pg/ml; normal range 2.4–21.9), and low angiotensin-converting enzyme (ACE) concentration (1.7 U/l; normal range 8.3–21.4). Taken together, these findings suggested an abnormality of the ACE gene, ACE. Direct sequencing analysis revealed two novel deletions in the coding region of ACE. We conclude that hormonal analysis of the renin-angiotensin system can aid in identifying the responsible genes and help with efficient gene analysis and pathophysiological considerations.