J Pediatr Endocr Met 2014; 27(11-12): 1101–1105
Hakan Cangul*, Veysel N. Bas, Yaman Saglam, Michaela Kendall, Timothy G. Barrett, Eamonn R. Maher and Zehra Aycan
A nonsense thyrotropin receptor gene mutation (R609X) is associated with congenital hypothyroidism and heart defects Abstract: Congenital hypothyroidism (CH), one of the most important preventable causes of mental retardation, is a clinical condition characterized by thyroid hormone deficiency in newborns. CH is most often caused by defects in thyroid development leading to thyroid dysgenesis. The thyroid-stimulating hormone receptor (TSHR) is the main known gene causing thyroid dysgenesis in consanguineous families with CH. In this study, we aim to determine the genetic alteration in a case with congenital hypothyroidism and heart defects coming from a consanguineous family. We utilized genetic linkage analysis and direct sequencing to achieve our aim. Our results revealed that the family showed linkage to the TSHR locus, and we detected a homozygous nonsense mutation (R609X) in the case. Apart from other cases with the same mutation, our case had accompanying cardiac malformations. Although cardiac malformations are not uncommon in sporadic congenital hypothyroidism, here, they are reported for the first time with R609X mutation in a familial case. Keywords: autosomal recessive; congenital heart defect; consanguineous; genetics; nonsense mutation; R609X; thyroid dysgenesis; TSHR.
*Corresponding author: Hakan Cangul, Department of Medical Genetics, Bahcesehir University School of Medicine, Istanbul, Turkey, Phone: +90 533 7449433, Fax: +90 216 4684567, E-mail: [email protected] Veysel N. Bas and Zehra Aycan: Division of Pediatric Endocrinology, Dr Sami Ulus Woman Health, Children Research Hospital, Ankara, Turkey Yaman Saglam: Centre for Genetic Diagnosis, Medical Park Goztepe Hospital, Istanbul, Turkey Michaela Kendall: Division of Clinical and Experimental Sciences, Faculty of Medicine, Department of Child Health, Southampton, UK Timothy G. Barrett: Centre for Rare Diseases and Personalised Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK Eamonn R. Maher: Academic Department of Medical Genetics, University of Cambridge Clinical School, Cambridge, UK
DOI 10.1515/jpem-2014-0025 Received January 18, 2014; accepted May 8, 2014; previously published online June 19, 2014
Introduction Congenital hypothyroidism (CH) is the most commonly encountered congenital endocrine disorder and is the most important cause of treatable mental retardation. Its incidence is approximately 1:3000–4000 live births (1, 2). Although the most common cause of hypothyroidism in the world, including its congenital forms in iodine deficiency, CH is commonly caused by defects in thyroid development leading to thyroid dysgenesis. Thyroid dysgenesis may be due to agenesis, hypoplasia, or ectopia of the gland (1–3). For non-goitrous congenital hypothyroidism (CHNG), four clinical entities with known causative genes have been described in the OMIM database to date (www.ncbi.nlm.nih.gov/omim), and the causative genes for these phenotypes are TSHR, PAX8, TSHB, NKX2-5 (2–5). We previously showed that the thyroid-stimulating hormone receptor (TSHR) was the main causative gene in autosomal recessively inherited thyroid dysgenesis (2). The human TSHR gene is located on chromosome 14q31 and the extracellular domain of the receptor is encoded by nine exons, whereas the transmembrane and intracellular portions are encoded by a single large exon that encode for a 765 amino acid protein. TSHR gene encodes for transmembrane receptor located in the follicular cell wall. TSH secreted from anterior pituitary mediates important effects of this gene on thyroid gland maturation and function. Expression of the TSHR gene is under the control of several factors, including the thyroid transcription factors 1 and 2 and PAX8. Most familial cases of TSH resistance are due to a loss of function mutations in the TSHR gene and have an autosomal recessive form of inheritance (1–3, 5). Congenital hypothyroidism predisposes an increased risk for additional congenital malformations for heart, kidneys, urinary system, gastrointestinal, and skeletal systems (6). Although this increase might be caused by
Brought to you by | University of California - San Francisco Authenticated Download Date | 2/17/15 9:46 AM
1102 Cangul et al.: A nonsense TSHR mutation metabolic effects of some abnormalities in thyroid hormones, it may also be caused by teratogen exposure to multiple organs, by thyroid deficiency, or iodine deficiency during organogenesis (6, 7). In thyroid dysgenesis cases, co-existing extra-thyroidal abnormalities are generally reported with TTF1 and TTF2, PAX8 mutations but not normally expected with TSHR mutations (1, 5). Here, we report a case with a nonsense TSHR mutation (R609X) who, unlike other cases carrying the same mutation, has accompanying cardiac anomalies.
Echocardiography revealed pulmonary stenosis (valvular) and atrial septal defect. In the last control at 8 years of age, his bone age was equal to 7 years. In his physical examination, his height was 125 cm [0.6 standard deviation (SD)]; the weight was 23 kg (–0.1 SD), and he had grade II/VI systolic ejection-type murmur in the pulmonary area. The patient had no mental retardation (intelligence quotient = 95 points) with Tanner stage 1 of puberty (bilateral testicular volumes were 2 mL). Hormonal evaluation showed normal serum levels of TSH (3.6 mlU/L), fT4 (1.4 ng/dL), fT3 (3.5 pg/mL), cortisol (12.6 ng/dL; normal, 5.5–25.0), and adrenocorticotropic hormone (31.5 ng/L; normal, 9.0–52.0). No thyroid gland was detectable during ultrasonography examination performed on two different occasions. Echocardiography revealed only pulmonary stenosis (valvular). The dose of thyroid hormone was adjusted according to weight and TSH levels during followup. Clinical and laboratory findings and L-thyroxine dose information until the last control visit of the case are given in Table 1.
Materials and methods Subject
Potential linkage analysis
The case, a 5-day-old male newborn who was referred with complaints of jaundice, was enrolled through our studies on the genetics of congenital hypothyroidism (2–4, 8–15). He was born via normal spontaneous route at 40 weeks of gestation with a birth weight of 3800 g and a length of 50 cm. He had no cyanosis after delivery and had been jaundice from the first days of life, however, this did not require any treatment. Family history showed parental consanguinity, where the parents were second-degree relatives (children of an aunt and an uncle), and there was no case of goiter in the family. Physical examination revealed a height of 49 cm, a weight of 2.95 kg (3rd–10th percentile), a head circumference of 34 cm (10th– 25th percentile), an anterior fontanelle of 3 × 3 cm, and a posterior fontanelle of 1 × 1 cm. Except for a grade II/VI systolic, ejection-type murmur in the pulmonary area, physical examination was within normal limits. Thyroid function test results showed a serum TSH of > 150 mlU/L (reference range: 0.35–5.5); a free thyroxine (fT4) level of 0.2 ng/dL (reference range: 0.8–2.0); and a free triiodothyronine (fT3) level of 1.5 pg/mL (reference range: 2–5). As no thyroid tissue was observed in thyroid ultrasonography and there was no activity in thyroid scintigraphy, the patient was diagnosed with athyreosis. L-thyroxine treatment at 10 μg/kg/day was introduced.
First, we performed linkage analysis to four known causative loci for CHNG phenotype in all family members with the use of microsatellite markers. Four primer pairs surrounding each locus were selected (Table 2). Fluorescent labelling of one oligonucleotide of each primer pair enabled the sizing of polymerase chain reaction (PCR) products in a capillary electrophoresis machine by the use of GeneMapper v4.0 software suite (Applied Biosystems, Warrington, UK). By combining genotypes for each microsatellite marker, we constructed haplotype tables for each family member. As autosomal recessive inheritance was assumed in consanguineous families, homozygosity of a particular haplotype for a locus in cases accompanied by heterozygosity of the same haplotype in both parents was taken as suggestive of linkage to that locus.
Direct sequence analysis of the TSHR gene The patient and his first-degree family members were investigated for the presence of TSHR mutations by conventional Sanger sequencing. The DNA template of the TSHR gene was downloaded from the Ensembl database (ENSG00000165409). All alternative protein
Table 1 Laboratory data and chronological and bone age of the patient. CA, d, m, y
TSH, mU/L (n: 0.5–5.6)
FT4, ng/dL (n: 0.9–2.3)
FT3, pg/mL (n: 2–5)
BA, y, m
5 d 3 m 1 y 2 y 3 y 4 y 5 y 6 y 7 y 8 y
> 150 1.75 4.2 3.7 8.2 3.9 2.6 4.8 2.1 3.6
T, in the gray rectangle, numbering according to Ensembl transcript ENST00000541158) in the case (upper panel).
fT4 levels; absence of antithyroid antibodies; normal or hypoplastic thyroid gland in ultrasonography examination; and positive family history for thyroid pathologies (5). Mutations resulting in inactivation of the TSH receptor were first reported in 1995 by Sunthornthepvarakul et al. in three sisters with asymptomatic hyperthyrotropinemia and thyroid glands of normal size and normal radioiodine uptake. None of the siblings had symptoms or signs of hypothyroidism at any time. There was no parental consanguinity; the parents were of different ethnic origin (16). The nonsense mutation R609X has originally been described in a large inbred Bedouin kindred, in which the cases had normally located hypoplastic thyroid glands accompanied by glucocorticoid deficiency (17). Therefore, it was recommended that cases with this mutation should be evaluated for hypocortisolemia. In contrast, Unruh et al. did not report glucocorticoid deficiency in Turkish patients with the same mutation, although normally located hypoplastic thyroid gland was similarly encountered (18). The absence of glucocorticoid deficiency in our patient suggested that the originally reported cases might be coincidental. While thyroid hormones have effects on growth, development, oxygen consumption and heat production,
nervous system functions, carbohydrate, lipid, protein, nucleic acid, vitamin, and inorganic ion metabolisms, their critical role is on the central nervous system (6, 7). In addition, extra-thyroidal abnormality incidence is increased in cases with congenital hypothyroidism. In a study performed on 1420 babies with congenital hypothyroidism, congenital malformation incidence was increased fourfold compared to the control group, and the most common malformation was cardiac. Other additional malformations were thorn like hair, cleft palate, neurological abnormalities, and genitourinary malformations (19). Gu et al. performed a study on 1520 cases with congenital hypothyroidism and reported extrathyroidal malformation ratio as 14.6%. They also noted that the most frequently accompanying malformations were cardiac (14.6%) (7). Stoll et al. defined extra-thyroidal abnormality in 10.5% of cases with primary persistent CH, and they defined congenital cardiac abnormalities fivefold (6.9%) higher than the normal population (20). In another study, ten of 76 (13.2%) patients with congenital hypothyroidism had major congenital malformations, and cardiac anomalies were defined in eight of them (21). In conclusion, this study emphasizes the role of detailed genetic analyses in definitive diagnosis and
Brought to you by | University of California - San Francisco Authenticated Download Date | 2/17/15 9:46 AM
Cangul et al.: A nonsense TSHR mutation 1105
accurate classification of familial CH and suggests that the nonsense R609X mutation in the TSHR gene could be accompanied by cardiac malformations.
References 1. Park SM, Chatterjee VK. Genetics of congenital hypothyroidism. J Med Genet 2005;42:379–89. 2. Cangul H, Aycan Z, Saglam H, Forman JR, Cetinkaya S, et al. TSHR is the main causative-locus in autosomal recessively inherited thyroid dysgenesis. J Pediatr Endocrinol Metabol 2012;25:419–26. 3. Cangul H, Morgan NV, Forman JR, Saglam H, Aycan Z, et al. Novel TSHR mutations in consanguineous families with congenital nongoitrous hypothyroidism. Clin Endocrinol (Oxf) 2010;73:671–7. 4. Baş VN, Cangul H, Agladioglu SY, Kendall M, Cetinkaya S, et al. Mild and severe congenital primary hypothyroidism in two patients with thyrotropine receptor (TSHR) gene mutation. J Pediatr Endocrinol Metab 2012;25:1153–6. 5. Cangul H, Schoenmakers NA, Saglam H, Doganlar D, Saglam Y, et al. A deletion including exon 2 of the TSHR gene is associated with thyroid dysgenesis and severe congenital hypothyroidism. J Pediatr Endocrinol Metab 2014;27:731–5. 6. Reddy PA, Rajagopal G, Harinarayan CV, Vanaja V, Rajasekhar D, et al. High prevalence of associated birth defects in congenital hypothyroidism. Int J Pediatr Endocrinol 2010;2010:940980. 7. Gu YH, Harada S, Kato T, Inomata H, Aoki K, et al. Increased incidence of extrathyroidal congenital malformations in Japanese patients with congenital hypothyroidism and their relationship with Down syndrome and other factors. Thyroid 2009;19:869–79. 8. Cangul H, Aycan Z, Olivera-Nappa A, Saglam H, Schoenmakers NA, et al. Thyroid dyshormonogenesis is mainly caused by TPO mutations in consanguineous community. Clin Endocrinol (Oxf) 2012;79:275–81. 9. Schoenmakers NA, Cangul H, Nicholas AK, Schoenmakers E, Lyons G, et al. A comprehensive next generation sequencingbased strategy for genetic diagnosis in congenital hypothyroidism. Endocrine Abstracts 2013;33:OC2.9. 10. Cangul H, Aycan Z, Kendall M, Bas VN, Saglam Y, et al. A truncating DUOX2 mutation (R434X) causes severe congenital hypothyroidism. J Pediatr Endocrinol Metab 2014;27:323–7.
11. Baş VN, Aycan Z, Cangul H, Kendall M, Ağladıoğlu SY, et al. A common thyroid peroxidase gene mutation (G319R) in Turkish patients with congenital hypothyroidism could be due to a founder effect. J Pediatr Endocrinol Metab 2014;27:383–7. 12. Cangul H, Boelaert K, Dogan M, Saglam Y, Kendall M, et al. Novel truncating thyroglobulin gene mutations associated with congenital hypothyroidism. Endocrine 2014;45:206–12. 13. Cangul H, Saglam H, Aycan Z, Yakut T, Gulten T, et al. Locus heterogeneity and novel TSHR mutations in consanguineous families with congenital non-goitrous hypothyroidism. J Med Genet 2010;47(Suppl 1):S59. 14. Cangul H, Morgan NV, Pasha S, Kirby GA, Karkucak M, et al. Genetic heterogeneity in congenital hypothyroidism. J Med Genet 2009;46(Suppl 1):S74. 15. Cangul H, Saglam H, Saglam Y, Eren E, Dogan D, et al. An essential splice site mutation (c.317+1G>A) in the TSHR gene leads to severe thyroid dysgenesis. J Pediatr Endocrinol Metab 2014;27:1021–5. 16. Sunthornthepvarakul T, Gottschalk ME, Hayashi Y, Refetoff S. Brief report: resistance to thyrotropin caused by mutations in the thyrotropin-receptor gene. N Engl J Med 1995;332: 155–60. 17. Tiosano D, Pannain S, Vassart G, Parma J, Gershoni-Baruch R, et al. The hypothyroidism in an inbred kindred with congenital thyroid hormone and glucocorticoid deficiency is due to a mutation producing a truncated thyrotropin receptor. Thyroid 1999;9:887–94. 18. Richter-Unruh A, Hauffa BP, Pfarr N, Pohlenz J. Congenital primary hypothyroidism in a Turkish family caused by a homozygous nonsense mutation (R609X) in the thyrotropin receptor gene. Thyroid 2004;14:971–4. 19. Olivieri A, Stazi MA, Mastroiacovo P, Fazzini C, Medda E, et al. A population-based study on the frequency of additional congenital malformations in infants with congenital hypothyroidism: data from the Italian Registry for Congenital Hypothyroidism (1991–1998). J Clin Endocrinol Metab 2002;87:557–62. 20. Stoll C, Dott B, Alembik Y, Koehl C. Congenital anomalies associated with congenital hypothyroidism. Ann Genet 1999;42:17–20. 21. Kreisner E, Neto EC, Gross JL. High prevalence of extrathyroid malformations in a cohort of Brazilian patients with permanent primary congenital hypothyroidism. Thyroid 2005;15:165–9.
Brought to you by | University of California - San Francisco Authenticated Download Date | 2/17/15 9:46 AM
Hakan Cangul*, Veysel N. Bas, Yaman Saglam, Michaela Kendall, Timothy G. Barrett, Eamonn R. Maher and Zehra Aycan
A nonsense thyrotropin receptor gene mutation (R609X) is associated with congenital hypothyroidism and heart defects Abstract: Congenital hypothyroidism (CH), one of the most important preventable causes of mental retardation, is a clinical condition characterized by thyroid hormone deficiency in newborns. CH is most often caused by defects in thyroid development leading to thyroid dysgenesis. The thyroid-stimulating hormone receptor (TSHR) is the main known gene causing thyroid dysgenesis in consanguineous families with CH. In this study, we aim to determine the genetic alteration in a case with congenital hypothyroidism and heart defects coming from a consanguineous family. We utilized genetic linkage analysis and direct sequencing to achieve our aim. Our results revealed that the family showed linkage to the TSHR locus, and we detected a homozygous nonsense mutation (R609X) in the case. Apart from other cases with the same mutation, our case had accompanying cardiac malformations. Although cardiac malformations are not uncommon in sporadic congenital hypothyroidism, here, they are reported for the first time with R609X mutation in a familial case. Keywords: autosomal recessive; congenital heart defect; consanguineous; genetics; nonsense mutation; R609X; thyroid dysgenesis; TSHR.
*Corresponding author: Hakan Cangul, Department of Medical Genetics, Bahcesehir University School of Medicine, Istanbul, Turkey, Phone: +90 533 7449433, Fax: +90 216 4684567, E-mail: [email protected] Veysel N. Bas and Zehra Aycan: Division of Pediatric Endocrinology, Dr Sami Ulus Woman Health, Children Research Hospital, Ankara, Turkey Yaman Saglam: Centre for Genetic Diagnosis, Medical Park Goztepe Hospital, Istanbul, Turkey Michaela Kendall: Division of Clinical and Experimental Sciences, Faculty of Medicine, Department of Child Health, Southampton, UK Timothy G. Barrett: Centre for Rare Diseases and Personalised Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, UK Eamonn R. Maher: Academic Department of Medical Genetics, University of Cambridge Clinical School, Cambridge, UK
DOI 10.1515/jpem-2014-0025 Received January 18, 2014; accepted May 8, 2014; previously published online June 19, 2014
Introduction Congenital hypothyroidism (CH) is the most commonly encountered congenital endocrine disorder and is the most important cause of treatable mental retardation. Its incidence is approximately 1:3000–4000 live births (1, 2). Although the most common cause of hypothyroidism in the world, including its congenital forms in iodine deficiency, CH is commonly caused by defects in thyroid development leading to thyroid dysgenesis. Thyroid dysgenesis may be due to agenesis, hypoplasia, or ectopia of the gland (1–3). For non-goitrous congenital hypothyroidism (CHNG), four clinical entities with known causative genes have been described in the OMIM database to date (www.ncbi.nlm.nih.gov/omim), and the causative genes for these phenotypes are TSHR, PAX8, TSHB, NKX2-5 (2–5). We previously showed that the thyroid-stimulating hormone receptor (TSHR) was the main causative gene in autosomal recessively inherited thyroid dysgenesis (2). The human TSHR gene is located on chromosome 14q31 and the extracellular domain of the receptor is encoded by nine exons, whereas the transmembrane and intracellular portions are encoded by a single large exon that encode for a 765 amino acid protein. TSHR gene encodes for transmembrane receptor located in the follicular cell wall. TSH secreted from anterior pituitary mediates important effects of this gene on thyroid gland maturation and function. Expression of the TSHR gene is under the control of several factors, including the thyroid transcription factors 1 and 2 and PAX8. Most familial cases of TSH resistance are due to a loss of function mutations in the TSHR gene and have an autosomal recessive form of inheritance (1–3, 5). Congenital hypothyroidism predisposes an increased risk for additional congenital malformations for heart, kidneys, urinary system, gastrointestinal, and skeletal systems (6). Although this increase might be caused by
Brought to you by | University of California - San Francisco Authenticated Download Date | 2/17/15 9:46 AM
1102 Cangul et al.: A nonsense TSHR mutation metabolic effects of some abnormalities in thyroid hormones, it may also be caused by teratogen exposure to multiple organs, by thyroid deficiency, or iodine deficiency during organogenesis (6, 7). In thyroid dysgenesis cases, co-existing extra-thyroidal abnormalities are generally reported with TTF1 and TTF2, PAX8 mutations but not normally expected with TSHR mutations (1, 5). Here, we report a case with a nonsense TSHR mutation (R609X) who, unlike other cases carrying the same mutation, has accompanying cardiac anomalies.
Echocardiography revealed pulmonary stenosis (valvular) and atrial septal defect. In the last control at 8 years of age, his bone age was equal to 7 years. In his physical examination, his height was 125 cm [0.6 standard deviation (SD)]; the weight was 23 kg (–0.1 SD), and he had grade II/VI systolic ejection-type murmur in the pulmonary area. The patient had no mental retardation (intelligence quotient = 95 points) with Tanner stage 1 of puberty (bilateral testicular volumes were 2 mL). Hormonal evaluation showed normal serum levels of TSH (3.6 mlU/L), fT4 (1.4 ng/dL), fT3 (3.5 pg/mL), cortisol (12.6 ng/dL; normal, 5.5–25.0), and adrenocorticotropic hormone (31.5 ng/L; normal, 9.0–52.0). No thyroid gland was detectable during ultrasonography examination performed on two different occasions. Echocardiography revealed only pulmonary stenosis (valvular). The dose of thyroid hormone was adjusted according to weight and TSH levels during followup. Clinical and laboratory findings and L-thyroxine dose information until the last control visit of the case are given in Table 1.
Materials and methods Subject
Potential linkage analysis
The case, a 5-day-old male newborn who was referred with complaints of jaundice, was enrolled through our studies on the genetics of congenital hypothyroidism (2–4, 8–15). He was born via normal spontaneous route at 40 weeks of gestation with a birth weight of 3800 g and a length of 50 cm. He had no cyanosis after delivery and had been jaundice from the first days of life, however, this did not require any treatment. Family history showed parental consanguinity, where the parents were second-degree relatives (children of an aunt and an uncle), and there was no case of goiter in the family. Physical examination revealed a height of 49 cm, a weight of 2.95 kg (3rd–10th percentile), a head circumference of 34 cm (10th– 25th percentile), an anterior fontanelle of 3 × 3 cm, and a posterior fontanelle of 1 × 1 cm. Except for a grade II/VI systolic, ejection-type murmur in the pulmonary area, physical examination was within normal limits. Thyroid function test results showed a serum TSH of > 150 mlU/L (reference range: 0.35–5.5); a free thyroxine (fT4) level of 0.2 ng/dL (reference range: 0.8–2.0); and a free triiodothyronine (fT3) level of 1.5 pg/mL (reference range: 2–5). As no thyroid tissue was observed in thyroid ultrasonography and there was no activity in thyroid scintigraphy, the patient was diagnosed with athyreosis. L-thyroxine treatment at 10 μg/kg/day was introduced.
First, we performed linkage analysis to four known causative loci for CHNG phenotype in all family members with the use of microsatellite markers. Four primer pairs surrounding each locus were selected (Table 2). Fluorescent labelling of one oligonucleotide of each primer pair enabled the sizing of polymerase chain reaction (PCR) products in a capillary electrophoresis machine by the use of GeneMapper v4.0 software suite (Applied Biosystems, Warrington, UK). By combining genotypes for each microsatellite marker, we constructed haplotype tables for each family member. As autosomal recessive inheritance was assumed in consanguineous families, homozygosity of a particular haplotype for a locus in cases accompanied by heterozygosity of the same haplotype in both parents was taken as suggestive of linkage to that locus.
Direct sequence analysis of the TSHR gene The patient and his first-degree family members were investigated for the presence of TSHR mutations by conventional Sanger sequencing. The DNA template of the TSHR gene was downloaded from the Ensembl database (ENSG00000165409). All alternative protein
Table 1 Laboratory data and chronological and bone age of the patient. CA, d, m, y
TSH, mU/L (n: 0.5–5.6)
FT4, ng/dL (n: 0.9–2.3)
FT3, pg/mL (n: 2–5)
BA, y, m
5 d 3 m 1 y 2 y 3 y 4 y 5 y 6 y 7 y 8 y
> 150 1.75 4.2 3.7 8.2 3.9 2.6 4.8 2.1 3.6
T, in the gray rectangle, numbering according to Ensembl transcript ENST00000541158) in the case (upper panel).
fT4 levels; absence of antithyroid antibodies; normal or hypoplastic thyroid gland in ultrasonography examination; and positive family history for thyroid pathologies (5). Mutations resulting in inactivation of the TSH receptor were first reported in 1995 by Sunthornthepvarakul et al. in three sisters with asymptomatic hyperthyrotropinemia and thyroid glands of normal size and normal radioiodine uptake. None of the siblings had symptoms or signs of hypothyroidism at any time. There was no parental consanguinity; the parents were of different ethnic origin (16). The nonsense mutation R609X has originally been described in a large inbred Bedouin kindred, in which the cases had normally located hypoplastic thyroid glands accompanied by glucocorticoid deficiency (17). Therefore, it was recommended that cases with this mutation should be evaluated for hypocortisolemia. In contrast, Unruh et al. did not report glucocorticoid deficiency in Turkish patients with the same mutation, although normally located hypoplastic thyroid gland was similarly encountered (18). The absence of glucocorticoid deficiency in our patient suggested that the originally reported cases might be coincidental. While thyroid hormones have effects on growth, development, oxygen consumption and heat production,
nervous system functions, carbohydrate, lipid, protein, nucleic acid, vitamin, and inorganic ion metabolisms, their critical role is on the central nervous system (6, 7). In addition, extra-thyroidal abnormality incidence is increased in cases with congenital hypothyroidism. In a study performed on 1420 babies with congenital hypothyroidism, congenital malformation incidence was increased fourfold compared to the control group, and the most common malformation was cardiac. Other additional malformations were thorn like hair, cleft palate, neurological abnormalities, and genitourinary malformations (19). Gu et al. performed a study on 1520 cases with congenital hypothyroidism and reported extrathyroidal malformation ratio as 14.6%. They also noted that the most frequently accompanying malformations were cardiac (14.6%) (7). Stoll et al. defined extra-thyroidal abnormality in 10.5% of cases with primary persistent CH, and they defined congenital cardiac abnormalities fivefold (6.9%) higher than the normal population (20). In another study, ten of 76 (13.2%) patients with congenital hypothyroidism had major congenital malformations, and cardiac anomalies were defined in eight of them (21). In conclusion, this study emphasizes the role of detailed genetic analyses in definitive diagnosis and
Brought to you by | University of California - San Francisco Authenticated Download Date | 2/17/15 9:46 AM
Cangul et al.: A nonsense TSHR mutation 1105
accurate classification of familial CH and suggests that the nonsense R609X mutation in the TSHR gene could be accompanied by cardiac malformations.
References 1. Park SM, Chatterjee VK. Genetics of congenital hypothyroidism. J Med Genet 2005;42:379–89. 2. Cangul H, Aycan Z, Saglam H, Forman JR, Cetinkaya S, et al. TSHR is the main causative-locus in autosomal recessively inherited thyroid dysgenesis. J Pediatr Endocrinol Metabol 2012;25:419–26. 3. Cangul H, Morgan NV, Forman JR, Saglam H, Aycan Z, et al. Novel TSHR mutations in consanguineous families with congenital nongoitrous hypothyroidism. Clin Endocrinol (Oxf) 2010;73:671–7. 4. Baş VN, Cangul H, Agladioglu SY, Kendall M, Cetinkaya S, et al. Mild and severe congenital primary hypothyroidism in two patients with thyrotropine receptor (TSHR) gene mutation. J Pediatr Endocrinol Metab 2012;25:1153–6. 5. Cangul H, Schoenmakers NA, Saglam H, Doganlar D, Saglam Y, et al. A deletion including exon 2 of the TSHR gene is associated with thyroid dysgenesis and severe congenital hypothyroidism. J Pediatr Endocrinol Metab 2014;27:731–5. 6. Reddy PA, Rajagopal G, Harinarayan CV, Vanaja V, Rajasekhar D, et al. High prevalence of associated birth defects in congenital hypothyroidism. Int J Pediatr Endocrinol 2010;2010:940980. 7. Gu YH, Harada S, Kato T, Inomata H, Aoki K, et al. Increased incidence of extrathyroidal congenital malformations in Japanese patients with congenital hypothyroidism and their relationship with Down syndrome and other factors. Thyroid 2009;19:869–79. 8. Cangul H, Aycan Z, Olivera-Nappa A, Saglam H, Schoenmakers NA, et al. Thyroid dyshormonogenesis is mainly caused by TPO mutations in consanguineous community. Clin Endocrinol (Oxf) 2012;79:275–81. 9. Schoenmakers NA, Cangul H, Nicholas AK, Schoenmakers E, Lyons G, et al. A comprehensive next generation sequencingbased strategy for genetic diagnosis in congenital hypothyroidism. Endocrine Abstracts 2013;33:OC2.9. 10. Cangul H, Aycan Z, Kendall M, Bas VN, Saglam Y, et al. A truncating DUOX2 mutation (R434X) causes severe congenital hypothyroidism. J Pediatr Endocrinol Metab 2014;27:323–7.
11. Baş VN, Aycan Z, Cangul H, Kendall M, Ağladıoğlu SY, et al. A common thyroid peroxidase gene mutation (G319R) in Turkish patients with congenital hypothyroidism could be due to a founder effect. J Pediatr Endocrinol Metab 2014;27:383–7. 12. Cangul H, Boelaert K, Dogan M, Saglam Y, Kendall M, et al. Novel truncating thyroglobulin gene mutations associated with congenital hypothyroidism. Endocrine 2014;45:206–12. 13. Cangul H, Saglam H, Aycan Z, Yakut T, Gulten T, et al. Locus heterogeneity and novel TSHR mutations in consanguineous families with congenital non-goitrous hypothyroidism. J Med Genet 2010;47(Suppl 1):S59. 14. Cangul H, Morgan NV, Pasha S, Kirby GA, Karkucak M, et al. Genetic heterogeneity in congenital hypothyroidism. J Med Genet 2009;46(Suppl 1):S74. 15. Cangul H, Saglam H, Saglam Y, Eren E, Dogan D, et al. An essential splice site mutation (c.317+1G>A) in the TSHR gene leads to severe thyroid dysgenesis. J Pediatr Endocrinol Metab 2014;27:1021–5. 16. Sunthornthepvarakul T, Gottschalk ME, Hayashi Y, Refetoff S. Brief report: resistance to thyrotropin caused by mutations in the thyrotropin-receptor gene. N Engl J Med 1995;332: 155–60. 17. Tiosano D, Pannain S, Vassart G, Parma J, Gershoni-Baruch R, et al. The hypothyroidism in an inbred kindred with congenital thyroid hormone and glucocorticoid deficiency is due to a mutation producing a truncated thyrotropin receptor. Thyroid 1999;9:887–94. 18. Richter-Unruh A, Hauffa BP, Pfarr N, Pohlenz J. Congenital primary hypothyroidism in a Turkish family caused by a homozygous nonsense mutation (R609X) in the thyrotropin receptor gene. Thyroid 2004;14:971–4. 19. Olivieri A, Stazi MA, Mastroiacovo P, Fazzini C, Medda E, et al. A population-based study on the frequency of additional congenital malformations in infants with congenital hypothyroidism: data from the Italian Registry for Congenital Hypothyroidism (1991–1998). J Clin Endocrinol Metab 2002;87:557–62. 20. Stoll C, Dott B, Alembik Y, Koehl C. Congenital anomalies associated with congenital hypothyroidism. Ann Genet 1999;42:17–20. 21. Kreisner E, Neto EC, Gross JL. High prevalence of extrathyroid malformations in a cohort of Brazilian patients with permanent primary congenital hypothyroidism. Thyroid 2005;15:165–9.
Brought to you by | University of California - San Francisco Authenticated Download Date | 2/17/15 9:46 AM
