Hyperthyroidism Caused by a Germline Activating Mutation of the Thyrotropin Receptor Gene: Difficulties in Diagnosis and Therapy

Abstract

Background:

Germline activating mutations of the thyrotropin receptor (TSHR) gene have been considered as the only known cause of sporadic nonautoimmune hyperthyroidism in the pediatric population. Here we describe the long-term follow-up and evaluation of a patient with sporadic nonautoimmune primary hyperthyroidism who was found to have a de novo germline activating mutation of the TSHR gene.

Summary:

The patient was an infant who presented at the age of 10 months in an unconscious state with exsiccation, wet skin, fever, and tachycardia. Nonautoimmune primary hyperthyroidism was diagnosed, and brain magnetic resonance imaging and computed tomography showed also Arnold-Chiari malformation type I. Continuous propylthiouracil treatment resulted in a prolonged clinical cure lasting for 10 years. At the age of 11 years and 5 months the patient underwent subtotal thyroidectomy because of symptoms of trachea compression caused by a progressive multinodular goiter. However, 2 months after surgery, hormonal evaluation indicated recurrent hyperthyroidism and the patient was treated with propylthiouracil during the next 4 years. At the age of 15 years the patient again developed symptoms of trachea compression. Radioiodine treatment resulted in a regression of the recurrent goiter and a permanent cure of hyperthyroidism without relapse during the last 3 years of his follow-up. Sequencing of exon 10 of the TSHR gene showed a de novo heterozygous germline I630L mutation, which has been previously described as activating mutation at somatic level in toxic thyroid nodules.

Conclusions:

The I630L mutation of the TSHR gene occurs not only at somatic level in toxic thyroid nodules, but also its presence in germline is associated with nonautoimmune primary hyperthyroidism. Our case report demonstrates that in this disorder a continuous growth of the thyroid occurs without any evidence of elevated TSH due to antithyroid drug overdosing. This may justify previous recommendations for early treatment of affected patients with removal of as much thyroid tissue as possible.

Introduction

N onautoimmune primary hyperthyroidism due to activating mutations of the thyrotropin receptor (TSHR) gene has been reported in 14 sporadic and 28 familial cases (1 –39). Clinical symptoms of this rare disorder may vary from severe fetal hyperthyroidism in prematurely born infants with potentially lethal complications to a symptomless subclinical hyperthyroidism (2,4,6,18,22,25,26,32). The size of the thyroid gland may be also variable (14). In addition, the onset of clinical manifestations in family members with the same mutation can be very diverse (22,36). Treatment with antithyroid drugs and subtotal thyroidectomy may control hyperthyroidism and thyroid tissue growth only for a limited period of time and, therefore, early diagnosis may be mandatory for providing a more effective treatment (12 –14).

Nonautoimmune primary hyperthyroidism may be associated with several clinical entities regardless of the type of TSHR gene mutations, but Arnold-Chiari malformation (ACM) has not been previously described in these patients (18). In this study, we present a long-term follow-up of a young patient with sporadic nonautoimmune primary hyperthyroidism and ACM type I (ACM1).

Patients and Methods

Case report

The patient was a male infant born at the 37th week after an uncomplicated gestation and was the first child of unrelated healthy Hungarian parents. The fetal heart rate was 150–170 beats/min during delivery, but after birth it returned to normal. His birth weight was 2700 g, his length was 50 cm, and head circumference was 31 cm. Neonatal screening for hypothyroidism based on TSH measurement failed to detect an abnormality, and neonatal blood spots for thyroid hormone measurements were not available when final diagnosis was established. There was no family history of any thyroid disorder. Somatic development of the patient was normal until the age of 4 months, but then a decreased weight gain was noted. At the age of 6 months he had Salmonella infection. At the age of 10 months he was hospitalized in an unconscious state with exsiccation, wet skin, fever, and tachycardia. On admission a mild exophthalmus (Hertel, 16–16/83 mm) was noted, but no thyroid enlargement or pretibial edema was observed. His weight was 6250 g (800 g below the third percentile) and his length was 72 cm (50 percentile). The fontanel was closed but craniosynostosis was absent.

Laboratory tests excluded Salmonella sepsis, and hyperthyroidism was diagnosed based on elevated levels of thyroid hormones with normal TSH (thyroxine [T4]: 45 μg/dL, normal range: 9–15; triiodothyronine [T3]: 525 ng/dL, normal range: 100–250; free T4 [fT4]: 7.3 ng/dL, normal range: 1.1–2.7; free T3 [fT3]: 15.4 pg/mL, normal range: 2.3–6.2; TSH: 1.2 mIU/L, normal range: 0.2–3.0; Table 1). Pituitary resistance to thyroid hormone and TSH-secreting pituitary tumor were considered but then excluded based on repeatedly suppressed rather than normal TSH levels. This raised the possibility that normal TSH at the time of admission was due to an analytical error. Radiological examination of the brain (magnetic resonance imaging [MRI] and computed tomography) detected hernia of tonsils to the foramen magnum and a mild ventriculomegaly presumably due to increased intracranial pressure. Thyroid ultrasonography showed normal-sized thyroid with hypoechogenic and inhomogeneous structure (Table 1). Thyroid scintigraphy indicated homogenous uptake within the thyroid gland. During TRH test, serum TSH values were below the normal range (<0.15 mU/L before as well as 20 and 60 minutes after TRH injection). Thyroid autoantibodies (antithyroglobulin, antithyroid peroxidase, and TSH receptor antibodies) were repeatedly negative both in the patient and in his mother. Repeat brain MRI performed a few days after admission showed ACM but the size of ventricles was normal. All these findings indicated that the clinical symptoms were caused by severe thyrotoxicosis.

Table 1.

Laboratory Data, Thyroid Volume, and Details of Treatment of a Patient with Nonautoimmune Primary Hyperthyroidism due to a Novel Germline Activating Mutation of the Thyrotropin Receptor Gene

Age	TSH (mU/L)	T4 (μg/dL)	T3 (ng/dL)	FT4 (ng/dL)	FT3 (pg/mL)	Daily dose of propylthiouracil (mg)	Thyroid volume (mL)
9 m		32				—	0.67
10 m	1.20^a	45	525	7.3	15.4	—
10 m	<0.15					50
10 m	<0.15	13.1				50
11 m	<0.15	26				50
11 m	<0.15	15				50
11 m	<0.15	14.6	300			50
11.5 m	<0.15	12.3	265			50
12 m	0.29	2.6	200			75
14 m	2.90	2.5	75			75
15 m	9.80	2.5	100			50
18 m	3.00	3				37.5
21 m	0.80	4.8	270			25
2 yr	0.88	3.8	235			25
2 yr 1 m						12.5
2 yr 3 m	0.15	12.4				12.5
2 yr 4 m	0.15	18.6				12.5	1.13
2 yr 4 m						25
2 yr 6 m	0.15	6.0	270			25
2 yr 10 m	<0.15	6.8	355			25
3 yr						37.5
3 yr 1 m						50
3 yr 10 m	<0.15	6.6	275	0.6		37.5
4 yr 11 m	0.33	5.0	198	0.5		37.5
6 yr	0.20	5.4	186	0.8		37.5
6 yr 5 m	0.10	8.9	177.7	1.1		37.5
8 yr 6 m	0.13	11.6	400.3	1.3		75
10 yr 6 m	0.01	12	405	1.7		100
11 yr 5 m	0.01	14.7				150	182.5
11 yr 5 m	Subtotal thyroidectomy					—
11 yr 7 m	0.01			3.3	9.4	—
11 yr 9 m	0.03			0.6	1.8	150
11 yr 10 m	1.34			0.3	1.8	150
12 yr	1.96			0.6	1.9	150
12 yr 1 m	1.03			0.8	2.9	150
12 yr 7 m	0.11			0.9		150
14 yr 8 m	0.03			1.4	4.4	150	12.1
15 yr 6 m	0.07			1.0	3.5	150
15 yr 7 m	Radioiodine treatment (400 MBq = 10.8 mCi ¹³¹I)					—
15 yr 8 m	0.01			1.3	2.9	—
16 yr	0.02			1.2		—
16 yr 2 m	0.05			1.4	2.9	—
16 yr 4 m	0.11			1.0	2.6	—
16 yr 5 m	0.20			1.1	2.6	—
16 yr 11 m	0.52			0.9	2.9	—
17 yr 3 m	0.37			1.4	3.6	—
17 yr 8 m	0.50			1.3	3.2	—	0.6

	Reference values (40)
Age	TSH (mU/L)	T4 (μg/dL)	T3 (ng/dL)	FT4 (ng/dL)	FT3 (pg/mL)
2–12 m	0.2–3.0	9–15	100–250	1.1–2.7	2.3–6.2
2–10 yr	0.2–3.0	6–12	90–240	1.0–2.3	2.3–6.2
11–20 yr	0.2–3.0	5–11	70–210	0.9–2.3	2.3–6.2

Analytical error cannot be excluded because of consistently suppressed TSH in next assays performed after a short period of time.

TSH, thyrotropin; FT4, free thyroxine; FT3, free triiodothyronine; m, months; yr, years.

After treatment for 2 weeks in intensive care unit (benzodiazepine, aminophenazone, dexamethasone, and glycerin for febrile seizures; increased intracranial pressure, propylthiouracil, and oxoprenolol for hyperthyroidism; and saline infusion supplemented with glucose and potassium), all symptoms disappeared and his general condition greatly improved. He was discharged from hospital and treatment with propylthiouracil (daily dose 50 mg) and oxoprenolol was continued. During the next 10 years the patient was treated with propylthiouracil and his TSH, T4, and T3 levels could be kept within or close to the normal range (Table 1). His psychosomatic development was normal and treatment was uneventful except that he developed a progressive goiter. At the age of 11 years and 5 months the patient underwent subtotal thyroidectomy because of symptoms of trachea compression. The resected thyroid tissue was 65 g, and the size of both lobes was 7 × 6 × 4 cm. Histopathological examination indicated multinodular hyperplasia with nodules containing follicular or papillary cells, but no signs of malignancy were observed.

Two months after surgery, hormonal evaluation again indicated suppressed TSH and increased fT4 and fT3 values, and the patient was treated with propylthiouracil during the next 4 years (Table 1). At the age of 15 years the patient again developed symptoms of trachea compression due to a recurrent goiter. After radioiodine treatment (400 MBq = 10.8 mCi ¹³¹I) performed at the age of 15½ years, serum fT4 and fT3 levels remained in the normal range without propylthiouracil treatment, but suppressed TSH was observed for more than 1 year. At present the patient is 18 years old, his height is 170 cm, and his weight is 65 kg. He is in a good general condition and his serum TSH, fT4, and fT3 levels are within the normal range without treatment. He has no symptoms of trachea compression and his recurrent goiter is partially regressed.

Molecular analysis of the TSHR gene

Genomic DNA was extracted from peripheral blood leukocytes from the patient and his parents using QIAamp Blood Kit (Qiagen, Hilden, Germany). DNA was also obtained from paraffin-embedded thyroid tissue specimens of the patient using QIAmp Tissue Kit (Qiagen). The mutation hotspot region located in exon 10 of the human TSHR gene was amplified with five sets of oligonucleotide primers. Oligonucleotide primers were designed using the Primer3 software. Primer sequences were as follows: 1F, 5′-GCCTGGCACTGACTCTTTTC-3′; 1R, 5′-GCCCATTATGTCTTCACACG-3′; 2F, 5′-TCAAAAACCCCCAGGAAGAG-3′; 2R, 5′-AGTGAAGAAACCAGCCGTGT-3′; 3F, 5′-TTTCTGCATGGGGATGTACC-3′; 3R, 5′-CTGGGTTGTACTGCGGATTT-3′; 4F, 5′-GTTTTTGTTCTGACGCTCAAC-3′; 4R, 5′-TGCTGTTCTTTGGAGGAACC-3′; 5F, 5′-ATTTTCACCAAGGCCTTCCA-3′; 5R, 5′-AGCTATGTGTTGGGGGTGTC-3′. PCR conditions were as follows: initial denaturation for 7 minutes at 95°C, followed by 35 cycles of denaturation for 45 seconds at 95°C, annealing for 45 seconds at 55°C, and elongation for 105 seconds at 72°C. The final elongation step lasted for 10 minutes at 72°C. Direct bidirectional sequencing was performed using ABI Genetic Analyser Model 3100 (Applied Biosystems, Foster, CA).

Results

Sequencing of exon 10 of the TSHR gene showed a heterozygous substitution of adenine to cytosine at nucleotide position 1888 in DNA samples obtained from both peripheral blood leukocytes and thyroid tissue specimens of the patient. This mutation results in a change of isoleucine to leucine at amino acid position 630. DNA sequencing indicated the absence of mutation in parents.

Discussion

In this study, we present the history of a young patient with sporadic nonautoimmune primary hyperthyroidism who was found to have a novel germline activating mutation of the TSHR gene (I630L). Its absence in his parents indicated that the mutation developed de novo in our patient. Interestingly, the I630L, located in the 6TM region of the TSHR, has not been previously reported as germline mutation but it has been already described at somatic level in toxic thyroid nodules (41 –43). Also, functional studies showed that heterozygous I630L represents a gain of function mutation, as COS-7 cells transfected with the I630L mutant displayed an increased basal and constitutive cAMP activity as well as a decreased expression of the mutant TSHR in cell surface compared with that observed after transfection with the wild-type TSHR gene. The basal inositol phosphate accumulation and binding of labeled TSH were similar in cells transfected with the I630L and wild-type TSHR gene, suggesting that activation of the cAMP pathway may play a crucial role in functional consequences of this mutation of the TSHR gene (44).

Because the growth and function of the thyroid gland is controlled by activation of the TSH receptor, gain of function mutations of the TSHR gene result in both hyperthyroidism and goiter. Although the size of goiter may be variable and it may be minimal or absent in young patients, once present, its continuous growth is frequently observed as in our patient (5,8). In our patient, thyroid growth occurred without any evidence of elevated TSH due to antithyroid drug overdosing, suggesting that constitutive activation of the mutant TSH receptor exerted a continuous stimulatory effect on the growth and proliferation of thyroid gland.

Lueblinghoff et al. analyzed genotype–phenotype correlations in a review of 14 patients with sporadic nonautoimmune primary hyperthyroidism (45). They found no consistent relationship between in vitro activity of the mutant TSH receptors and the clinical course of the disease, suggesting that other genetic, epigenetic, and/or environmental modifiers may play a role (45).

In several earlier reports the first choice of treatment was an antithyroid drug that could effectively control disease symptoms for the first 5 or 10 years (3,7). Subtotal or total thyroidectomy has been performed in several cases, especially when antithyroid drugs proved to be ineffective or in cases with multinodular goiter (1,38). Multinodular goiter may also predispose for the development of thyroid neoplasia (28). In some cases with recurrent goiter, a second thyroid surgery or radioiodine therapy has been carried out (5,12 –14,18,26). Total thyroidectomy combined with radioiodine therapy has been also reported for controlling the disease (5,12,13). Nevertheless, it is reasonable to consider the recommendation of Paschke and Ludgate, who proposed that patients with germline TSHR mutations should be treated early by removing as much thyroid tissue as possible to control the hyperthyroidism permanently and avoid relapses (46).

It is interesting that at the time of diagnosis the brain MRI in our patient showed that the tonsils of the cerebellum extend below the foramen magnum, indicating the presence of ACM1. Although this malformation may lead to a variety of neurological complications, our patient remained symptomless during his follow-up. The underlying cause of ACM1 is unknown but its familial aggregation suggests a genetic component (47). Recently, Boyles et al. identified candidate loci on chromosome 9q22.31 and 15q21.1–q22.3 by genome-wide linkage analysis of 71 individuals from 23 families with ACM1 (48). ACM has not been previously described in patients with nonautoimmune primary hyperthyroidism, and therefore, it is not known whether the presence of both disorders in our patient could have a pathogenic link or they simply represent a coincidence of two rare disorders.

In conclusion, our patient with nonautoimmune primary hyperthyroidism had a germline mutation of the TSHR gene (I630L), which has been previously proved to be an activating mutation at somatic level. After a prolonged treatment with propylthiouracil and subtotal thyroidectomy, the patient was treated with radioiodine, which resulted in a permanent cure of hyperthyroidism without relapse during the last 3 years of his follow-up. This case report demonstrates that in this disorder a continuous growth of the thyroid occurs without any evidence of elevated TSH due to antithyroid drug overdosing, which may justify previous recommendations for early treatment of affected patients by removing as much thyroid tissue as possible to control the disorder.

Footnotes

Acknowledgments

This work was supported by grants from the Hungarian Ministry of Public Health (EET 090/2006) and by the Regional University Center of Excellence in Environmental Industry Based on Natural Resource, Szent István University (Pázmány, RET-12/2005; Baross, KMKINNOV). Attila Patócs is a recipient of Bolyai János Research Fellowship.

Disclosure Statement

The authors declare that no competing financial interests exist.

References

Grüters

, Schöneberg

, Biebermann

, Krude

, Krohn

, Dralle

, Gudermann

. 1998. Severe congenital hyperthyroidism caused by a germ-line neo mutation in the extracellular portion of the thyrotropin receptor. J Clin Endocrinol Metab, 83:1431–1436.

Chester

, Rotenstein

, Ringkananont

, Steuer

, Carlin

, Stewart

, Grasberger

, Refetoff

. 2008. Congenital neonatal hyperthyroidism caused by germline mutations in the TSH receptor gene. J Pediatr Endocrinol Metab, 21:479–486.

Börgel

, Pohlenz

, Koch

, Bramswig

. 2005. Long-term carbimazole treatment of neonatal nonautoimmune hyperthyroidism due to a new activating TSH receptor gene mutation (Ala428Val) Horm Res, 64:203–208.

de Roux

, Polak

, Couet

, Leger

, Czernichow

, Milgrom

, Misrahi

. 1996. A neomutation of the thyroid-stimulating hormone receptor in a severe neonatal hyperthyroidism. J Clin Endocrinol Metab, 81:2023–2026.

Lavard

, Sehested

, Brock Jacobsen

, Muller

, Perrild

, Feldt-Rasmussen

, Parma

, Vassart

. 1999. Long-term follow up of an infant with thyrotoxicosis due to germline mutation of the TSH receptor gene (Met453Thr) Horm Res, 51:43–46.

Holzapfel

, Wonerow

, von Petrykowski

, Henschen

, Scherbaum

, Paschke

. 1997. Sporadic congenital hyperthyroidism due to a spontaneous germline mutation in the thyrotropin receptor gene. J Clin Endocrinol Metab, 82:3879–3884.

Führer

, Mix

, Wonerow

, Richter

, Willgerodt

, Paschke

. 1999. Variable phenotype associated with Ser505Asn-activating thyrotropin-receptor germline mutation. Thyroid, 9:757–761.

Nishihara

, Fukata

, Hishinuma

, Kudo

, Ohye

, Ito

, Kubota

, Amino

, Kuma

, Miyauchi

. 2006. Sporadic congenital hyperthyroidism due to a germline mutation in the thyrotropin receptor gene (Leu512Gln) in a Japanese patient. Endocr J, 53:735–740.

Tonacchera

, Agretti

, Rosellini

, Ceccarini

, Perri

, Zampolli

, Longhi

, Larizza

, Pinchera

, Vitti

, Chiovato

. 2000. Sporadic nonautoimmune congenital hyperthyroidism due to a strong activating mutation of the thyrotropin receptor gene. Thyroid, 10:859–863.

10.

Watkins

, Dejkhamron

, Huo

, Vazquez

, Menon

. 2008. Persistent neonatal thyrotoxicosis in a neonate secondary to a rare thyroid-stimulating hormone receptor activating mutation: case report and literature review. Endocr Pract, 14:479–483.

11.

Esapa

, Duprez

, Ludgate

, Mustafa

, Kendall-Taylor

, Vassart

, Harris

. 1999. A novel thyrotropin receptor mutation in an infant with severe thyrotoxicosis. Thyroid, 9:1005–1010.

12.

Kopp

, van Sande

, Parma

, Duprez

, Gerber

, Joss

, Jameson

, Dumont

, Vassart

. 1995. Brief report: congenital hyperthyroidism caused by a mutation in the thyrotropin-receptor gene. N Engl J Med, 332:150–154.

13.

Kopp

, Jameson

, Roe

. 1997. Congenital nonautoimmune hyperthyroidism in a nonidentical twin caused by a sporadic germline mutation in the thyrotropin receptor gene. Thyroid, 7:765–770.

14.

Bircan

, Miehle

, Mladenova

, Ivanova

, Sarafova

, Borissova

, Lüblinghoff

, Paschke

. 2008. Multiple relapses of hyperthyroidism after thyroid surgeries in a patient with long term follow-up of sporadic non-autoimmune hyperthyroidism. Exp Clin Endocrinol Diabetes, 116:341–346.

15.

Guemas

, Guorguleva

, Rothenbuler

, Stuckens

, Weill

, Cartigny

. 2003. Hyperthyroidism due to an activating mutation of the thyrotropin receptor. Horm Res, 60,Suppl 2:98–99.

16.

Biebermann

, Schöneberg

, Hess

, Germak

, Gudermann

, Grüters

. 2001. The first activating TSH receptor mutation in transmembrane domain 1 identified in a family with nonautoimmune hyperthyroidism. J Clin Endocrinol Metab, 86:4429–4433.

17.

Elgadi

, Arvidsson

, Janson

, Marcus

, Costagliola

, Norgren

. 2005. Autosomal-dominant non-autoimmune hyperthyroidism presenting with neuromuscular symptoms. Acta Paediatr, 94:1145–1161.

18.

Supornsilchai

, Sahakitrungruang

, Wongjitrat

, Wacharasindhu

, Suphapeetiporn

, Shotelersuk

. 2009. Expanding clinical spectrum of non-autoimmune hyperthyroidism due to an activating germline mutation, p.M453T, in the thyrotropin receptor gene. Clin Endocrinol (Oxf ), 70:623–628.

19.

Fuhrer

, Warner

, Sequeira

, Paschke

, Gregory

, Ludgate

. 2000. Novel TSHR germline mutation (Met463Val) masquerading as Graves' disease in a large Welsh kindred with hyperthyroidism. Thyroid, 10:1035–1041.

20.

Lee

, Poh

, Loke

. 2002. An activating mutation of the thyrotropin receptor gene in hereditary non-autoimmune hyperthyroidism. J Pediatr Endocrinol Metab, 15:211–215.

21.

Arturi

, Chiefari

, Tumino

, Russo

, Squatrito

, Chazenbalk

, Persani

, Rapoport

, Filetti

. 2002. Similarities and differences in the phenotype of members of an Italian family with hereditary non-autoimmune hyperthyroidism associated with an activating TSH receptor germline mutation. J Endocrinol Invest, 25:696–701.

22.

Ferrara

, Capalbo

, Rossi

, Capuano

, Del Prete

, Esposito

, Montesano

, Zampella

, Fenzi

, Salerno

, Macchia

. 2007. A new case of familial nonautoimmune hyperthyroidism caused by the M463V mutation in the TSH receptor with anticipation of the disease across generations: a possible role of iodine supplementation. Thyroid, 17:677–680.

23.

Akcurin

, Turkkahraman

, Tysoe

, Ellard

, De Leener

, Vassart

, Costagliola

. 2008. A family with a novel TSH receptor activating germline mutation (p.Ala485Val) Eur J Pediatr, 167:1231–1237.

24.

Tonacchera

, Van Sande

, Cetani

, Swillens

, Schvartz

, Winiszewski

, Portmann

, Dumont

, Vassart

, Parma

. 1996. Functional characteristics of three new germline mutations of the thyrotropin receptor gene causing autosomal dominant toxic thyroid hyperplasia. J Clin Endocrinol Metab, 81:547–554.

25.

Pohlenz

, Pfarr

, Krüger

, Hesse

. 2006. Subclinical hyperthyroidism due to a thyrotropin receptor (TSHR) gene mutation (S505R) Acta Paediatr, 95:1685–1687.

26.

Vaidya

, Campbell

, Tripp

, Spyer

, Hattersley

, Ellard

. 2004. Premature birth and low birth weight associated with nonautoimmune hyperthyroidism due to an activating thyrotropin receptor gene mutation. Clin Endocrinol (Oxf ), 60:711–718.

27.

Duprez

, Parma

, Van Sande

, Allgeier

, Leclère

, Schvartz

, Delisle

, Decoulx

, Orgiazzi

, Dumont

, Vassart

. 1994. Germline mutations in the thyrotropin receptor gene cause non-autoimmune autosomal dominant hyperthyroidism. Nat Genet, 7:396–401.

28.

Karges

, Krause

, Homoki

, Debatin

, de Roux

, Karges

. 2005. TSH receptor mutation V509A causes familial hyperthyroidism by release of interhelical constraints between transmembrane helices TMH3 and TMH5. J Endocrinol, 186:377–385.

29.

Biebermann

, Krude

, Kohler

, Huhne

, Dralle

, Kohn

. 1996. A novel germline mutation of the thyrotropin receptor gene leading to familial hyperthyroidism with different penetrance. J Endocrinol Invest, 19,(Suppl 6):143–172.

30.

Claus

, Maier

, Paschke

, Kujat

, Stumvoll

, Führer

. 2005. Novel thyrotropin receptor germline mutation (Ile568Val) in a Saxonian family with hereditary nonautoimmune hyperthyroidism. Thyroid, 15:1089–1094.

31.

Alberti

, Proverbio

, Costagliola

, Weber

, Beck-Peccoz

, Chiumello

, Persani

. 2001. A novel germline mutation in the TSH receptor gene causes nonautoimmune autosomal dominant hyperthyroidism. Eur J Endocrinol, 145:249–254.

32.

Nishihara

, Nagayama

, Amino

, Hishinuma

, Takano

, Yoshida

, Kubota

, Fukata

, Kuma

, Miyauchi

. 2007. A novel thyrotropin receptor germline mutation (Asp617Tyr) causing hereditary hyperthyroidism. Endocr J, 54:927–934.

33.

Schwab

, Gerlich

, Broecker

, Söhlemann

, Derwahl

, Lohse

. 1997. Constitutively active germline mutation of the thyrotopin receptor gene as a cause of congenital hyperthyroidism. J Pediatr, 131:899–904.

34.

Ringkananont

, Van Durme

, Montanelli

, Ugrasbul

, Yu

, Weiss

, Refetoff

, Grasberger

. 2006. Repulsive separation of the cytoplasmic ends of transmembrane helices 3 and 6 is linked to receptor activation in a novel thyrotropin receptor mutant (M626I) Mol Endocrinol, 20:893–903.

35.

Führer

, Wonerow

, Willgerodt

, Paschke

. 1997. Identification of a new thyrotropin receptor germline mutation (Leu629Phe) in a family with neonatal onset of autosomal dominant nonautoimmune hyperthyroidism. J Clin Endocrinol Metab, 82:4234–4238.

36.

Nwosu

, Gourgiotis

, Gershengorn

, Neumann

. 2006. A novel activating mutation in transmembrane helix 6 of the thyrotropin receptor as cause of hereditary nonautoimmune hyperthyroidism. Thyroid, 16:505–512.

37.

Biebermann

, Schöneberg

, Krude

, Gudermann

, Grüters

. 2000. Constitutively activating TSH-receptor mutations as a molecular cause of non-autoimmune hyperthyroidism in childhood. Langenbecks Arch Surg, 385:390–392.

38.

Khoo

, Parma

, Rajasoorya

, Ho

, Vassart

. 1999. A germline mutation of the thyrotropin receptor gene associated with thyrotoxicosis, mitral valve prolapse in a Chinese family. J Clin Endocrinol Metab, 84:1459–1462.

39.

Liu

, Sun

, Dong

, He

, Cheng

CHK

, Fan

. 2008. A novel TSHR gene mutation (Ile691Phe) in a Chinese family causing autosomal dominant non-autoimmune hyperthyroidism. J Hum Genet, 53:475–478.

40.

Sólyom

, Wudy

, Homoki

. 1997. Hormondiagnostik im Kindesalter. Hans Marseille Verlag GmbH: München, 49–52.

41.

Holzapfel

, Führer

, Wonerow

, Weinland

, Scherbaum

, Paschke

. 1997. Identification of constitutively activating somatic thyrotropin receptor mutations in a subset of toxic multinodular goiters. J Clin Endocrinol Metab, 82:4229–4233.

42.

Farid

, Kascur

, Balazs

. 2000. The human thyrotropin receptor is highly mutable: a review of gain-of-function mutations. Eur J Endocrinol, 143:25–30.

43.

Gozu

, Avsar

, Bircan

, Claus

, Sahin

, Sezgin

, Deyneli

, Paschke

, Cirakoglu

, Akalin

. 2005. Two novel mutations in the sixth transmembrane segment of the thyrotropin receptor gene causing hyperfunctioning thyroid nodules. Thyroid, 15:389–397.

44.

Wonerow

, Chey

, Führer

, Holzapfel

, Paschke

. 2000. Functional characterization of five constitutively activating thyrotropin receptor mutations. Clin Endocrinol (Oxf ), 53:461–468.

45.

Lueblinghoff

, Mueller

, Sontheimer

, Paschke

. 2009. Lack of consistent association of TSH receptor mutations in vitro activity with the clinical course of patients with sporadic non-autoimmune. J Endocrinol Invest2009 Jul 28 [Epub ahead of print].

46.

Paschke

, Ludgate

. 1997. The thyrotropin receptor in thyroid diseases. N Engl J Med, 337:1675–1681.

47.

Milhorat

, Chou

, Trinidad

, Kula

, Mandell

, Wolpert

, Speer

. 1999. Chiari I malformation redefined: clinical and radiographic findings for 364 symptomatic patients. Neurosurgery, 44:1005–1017.

48.

Boyles

, Enterline

, Hammock

, Siegel

, Slifer

, Mehltretter

, Gilbert

, Hu-Lince

, Stephan

, Batzdorf

, Benzel

, Ellenbogen

, Green

, Kula

, Menezes

, Mueller

, Oro’

, Iskandar

, George

, Milhorat

, Speer

. 2006. Phenotypic definition of Chiari type I malformation coupled with high-density SNP genome screen shows significant evidence for linkage to regions on chromosomes 9 and 15. Am J Med Genet Part A, 140:2776–2785.