Genetic analysis of TTF-2 gene in children with congenital hypothyroidism and cleft palate, congenital hypothyroidism, or isolated cleft palate

Does the Polymorphism in the Length of the Polyalanine Tract of FOXE1 Gene Influence the Risk of Thyroid Dysgenesis Occurrence?

Background. Recent data have suggested that polymorphisms in the length of the polyalanine tract (polyA) of FOXE1 gene may act as a susceptibility factor for thyroid dysgenesis. The main purpose of this study was to investigate the influence of polyA of FOXE1 gene on the risk of thyroid dysgenesis. Method. A case-control study was conducted in a sample of 90 Brazilian patients with thyroid dysgenesis and 131 controls without family history of thyroid disease. Genomic DNA was isolated from peripheral blood samples and the genotype of each individual was determined by automated sequencing. Results. More than 90% of genotypes found in the group of patients with thyroid dysgenesis and in controls subjects were represented by sizes 14 and 16 polymorphisms in the following combinations: 14/14, 14/16, and 16/16. Genotypes 14/16 and 16/16 were more frequent in the control group, while genotype 14/14 was more frequent in the group of patients with thyroid dysgenesis. There was no difference between agenesis group and control group. Genotype 14/14 when compared to genotypes 14/16 and 16/16A showed an association with thyroid dysgenesis. Conclusion. PolyA of FOXE1 gene alters the risk of thyroid dysgenesis, which may explain in part the etiology of this disease.

Permanent and Transient Congenital Hypothyroidism in Hamadan West Province of Iran

BACKGROUND

Primary congenital hypothyroidism (CH) is the most common treatable cause of mental retardation and can be classified into permanent and transient types. The purpose of this study was to determine the prevalence of permanent and transient congenital hypothyroidism (CH) in Hamadan, West province of Iran.

METHODS

The study population included all cases with primary congenital hypothyroidism, which were confirmed by thyroid function tests (TSH levels ≥ 10 mIU/L). All these patients had been followed up at the outpatient pediatric endocrine clinic of Besat hospital (Hamadan, Iran) for a period of time between May 2006 and March 2013. Biochemical findings at diagnosis and detailed medical records were collected. Patients were considered as permanent hypothyroidism if their TSH level was 10 (mIU/l) during 6 - 12 months of treatment. Also three years old patients with TSH level > 10 mU/L during one or three months after discontinuation of levothyroxine treatment were considered as permanent hypothyroidism.

RESULTS

A total of 164 children (49.9% male and 50.6% female) diagnosed with CH completed the study. Female/male ratio was 1.02/1. The incidence of CH was about 1/1250 in Hamadan, West province of Iran. Of the 164 patients, 105 cases (64 %) were diagnosed as permanent CH and other 59 cases (36%) were proven to have transient hypothyroidism. Female to male ratio was 1.14 in patients suffering from permanent CH and 0.8 in patients with transient CH. The initial TSH level was found to be significantly higher in cases with permanent CH compared to the patients with transient CH (P = 0.001). Mean TSH level during the first year of treatment was higher in permanent CH cases compared to transient cases (P = 0.001). Children with transient CH had a lower TSH serum level during the three years of treatment (P = 0.000). A significant statistical difference was not found between the genders and permanent or transient CH (P = 0.352). Co-occurring congenital anomalies and birth order were significantly different between two groups (P = 0.028 and P = 0.024, respectively).

CONCLUSIONS

Our regional follow-up data showed that about 40% of newborns with primary CH had transient thyroid dysfunction. Our results further clarify our previous research by providing evidences on the incidence rate of CH. The incidence rates of CH as well as transient type of CH in our region were higher than those reported by other studies which have been conducted in other regions of the world. The initial TSH level was the strongest predictor of treatment cessation. Given the high incidence of transient CH in our region, further studies are needed to confirm the etiology and to provide considerable insight into preventive and/or the treatment strategies.

Frequency and effect on serum TSH of phosphodiesterase 8B (PDE8B) gene polymorphisms in patients with sporadic nonautoimmune subclinical hypothyroidism

BACKGROUND

Nonautoimmune subclinical hypothyroidism (NSH) is characterized by elevated serum TSH in presence of normal thyroid hormone levels and absence of anti-thyroid antibodies. As result of a genomic-wide study, a strong association between three polymorphic variants in intron 1 of human PDE8B gene (rs4704397, rs6885099, rs2046045) and serum TSH has been reported in euthyroid subjects.

AIM

The aim of this study was to evaluate frequency and effects on serum TSH of PDE8B gene polymorphisms in patients with sporadic NSH and verify if differences in serum TSH levels are associated to these polymorphic variants.

SUBJECTS AND METHODS

A total of 58 Italian selected patients affected by NSH, with elevated serum TSH, normal FT3 and FT4 and without TSHr gene mutations, were subjected to genotyping for specific single nucleotide polymorphism of PDE8B gene.

RESULTS

In all patients, the integrity of TSH receptor gene was attested. The ancestral allele associated with increased serum TSH was present in 42/58 patients (72.4 %) for rs4704397, in 42/58 patients (72.4 %) for rs6885099 and in 44/58 patients (75.9 %) for rs2046045. However, similar values of serum TSH were detected in patients with minor or major allele for each polymorphism.

CONCLUSIONS

A prevalence of the minor allele of PDE8B gene polymorphism associated with elevated serum levels of TSH was demonstrated in patients affected by sporadic NSH; however, significant differences in circulating TSH in patients with minor or major alleles for each polymorphism were not identified demonstrating the lack of association between the polymorphisms and serum TSH levels in these patients.

Congenital hypothyroidism caused by a novel homozygous mutation in the thyroglobulin gene

Congenital hypothyroidism (CH) due to thyroglobulin (TG) deficit is an autosomal recessive disease (OMIM #274700) characterized by hypothyroidism, goiter, low serum TG, and a negative perchlorate discharge test. The aim of this study was to perform the genetic analysis of the TG gene in two sisters born from consanguineus parents and affected by CH and low serum TG levels. The index patient and her sister were identified at neonatal screening for CH and treated with L-thyroxine (L-T4). After discontinuation of L-T4 therapy, hypothyroidism was confirmed, serum TG was undetectable, and no organification defect after (123)I scintigraphy and perchlorate test was shown; thyroid ultrasound showed a eutopic gland of normal size. DNA was extracted from peripheral white blood cells of the two sisters and the father. All 48 exons of TG gene were amplified by polymerase chain reaction and subjected to direct sequencing. A novel homozygous point mutation in exon 10 of TG gene was identified in the patient and her sister. The mutation determined a stop codon at position 768 (R768X) resulting in an early truncated protein or in the complete absence of the protein. The father (euthyroid) was heterozygous carrier of the mutation.

CONCLUSION

Genetic analysis of TG gene was performed in two sisters affected by CH. A novel point mutation of the TG gene determining a stop codon at position 768 of the protein was identified. The early truncated nonfunctioning protein or the absence of the protein due to the premature degradation of abnormal mRNA may be responsible of the observed phenotype.

Permanent and transient congenital hypothyroidism in Fayoum, Egypt: a descriptive retrospective study

BACKGROUND

Congenital hypothyroidism (CH) is one of the most common preventable causes of mental retardation. One important challenge in understanding the epidemiology of CH is that some newborns will have transient CH, a temporary depression of thyroid hormone concentrations that can last from several days to several months. Studies from other countries have reported that 10 to 15% of children treated for CH ultimately prove not to need treatment past 3 years of age to maintain normal hormone concentrations, and thus have transient hypothyroidism. The purpose of this study was to determine the prevalence of permanent and transient congenital hypothyroidism in Fayoum, Egypt.

METHODS

Cases detected by Fayoum neonatal screening program (NSP) between January 2003 and December 2011, and followed up at health insurance center were included. Permanent or transient CH was determined using results of thyroid function tests.

RESULTS

Of the 248 patients diagnosed primarily with CH by NSP; 204 (82.3%) patients were diagnosed to have permanent CH (prevalence 1/3587 live birth), and 44 (17.7%) patients were diagnosed to have transient CH (prevalence 1/16667 live birth). Initial TSH levels were higher in permanent CH cases than transient cases (p<0.004). Female to male ratio was 0.8 and 0.7 in permanent and transient CH respectively. 161 (65%) patients had thyroid dysgenesis (107 ectopic thyroid gland, 28 athyreosis and 26 thyroid hypoplasia). 87 (35%) patients had intact gland in thyroid scan and were considered to have dyshormonogenesis. Of these 87 patients 44 proved to have transient CH and 43 had permanent CH.

CONCLUSION

The preliminary data from our study revealed that the incidences of CH as well as the permanent form were similar to worldwide reports. Although the high incidence of transient CH in our study could be explained by iodine deficiency further studies are needed to confirm the etiology and plan the treatment strategies.

FOXE1 polymorphisms are associated with familial and sporadic nonmedullary thyroid cancer susceptibility

OBJECTIVE

FOXE1 is a transcription factor required for thyroid differentiation and function. FOXE1 locus polymorphisms (chromosome 9q22.33) were recently associated with increased sporadic thyroid cancer risk. In this study, we aimed to investigate the association of FOXE1 variants with nonmedullary thyroid cancer (NMTC), in both sporadic and familial (FNMTC) cases from the Portuguese population.

DESIGN AND METHODS

Nine variants located at the FOXE1 locus were sequenced in genomic DNA from 60 FNMTC probands and 80 patients with sporadic NMTC. Alleles were tested for association with thyroid cancer, against 130 healthy matched Portuguese controls.

RESULTS

All variants were significantly associated with increased thyroid cancer risk when combining familial and sporadic cases (OR range = 1·62-2·58). In particular, two reported risk variants were associated with the disease: rs965513 (allele A) with familial (OR = 2·30, 95% CI = 1·48-3·59, P = 0·0002) and sporadic (OR = 2·81, 95% CI = 1·87-4·22, P < 0·0001) NMTC and rs1867277 (allele A) with the sporadic (OR = 1·76, 95% CI = 1·18-2·62, P = 0·0052) and combined NMTC cases (OR = 1·70, 95% CI = 1·21-2·40, P = 0·0022). Interestingly, we also identified association of FOXE1 polyalanine tract expansions (>14 alanines) with thyroid cancer risk, in both familial (OR = 2·56, 95% CI = 1·64-4·01, P < 0·0001) and sporadic (OR = 2·44, 95% CI = 1·61-3·68, P < 0·0001) cases.

CONCLUSIONS

We found compelling evidence of association between FOXE1 variants and thyroid cancer risk in the Portuguese population. To our knowledge, this is the first study supporting the association of this locus with both sporadic and familial NMTC susceptibility.

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.

[New aspects of genetics and molecular mechanisms on thyroid morphogenesis for the understanding of thyroid dysgenesia]

The elucidation of the molecular mechanisms underlying the very early steps of thyroid organogenesis and the etiology of most cases of thyroid dysgenesis are poorly understood. Many genes have been identified as important contributors to survival, proliferation and migration of thyroid cells precursors, acting as an integrated and complex regulatory network. Moreover, by generation of mouse mutants, the studies have provided better knowledge of the role of these genes in the thyroid morphogenesis. In addition, it is likely that a subset of patients has thyroid dysgenesis as a result of mutations in regulatory genes expressed during embryogenesis. This review summarizes molecular aspects of thyroid development, describes the animal models and phenotypes known to date and provides information about novel insights into the ontogeny and pathogenesis of human thyroid dysgenesis.

Permanent and transient congenital hypothyroidism in Isfahan-Iran

OBJECTIVES

To determine the prevalence of permanent and transient congenital hypothyroidism (CH) in Isfahan, Iran.

METHODS

In 256 primarily diagnosed CH patients identified through the neonatal screening programme from May 2002 to February 2005, treatment was discontinued for 4 weeks and T4 and thyroid stimulating hormone (TSH) were measured. Permanent or transient CH was determined from the results of the thyroid function tests and the radiologic findings. Patients with TSH levels >6 (mIU/l) were diagnosed with permanent CH.

RESULTS

Results were available from 204 patients, of whom 122 patients were diagnosed with permanent CH (59.8%) (prevalence 1:748 births), and 82 with transient hypothyroidism (prevalence 1:1114). Permanent CH was associated with higher initial TSH levels than transient hypothyroidism (P < 0.05). The most common aetiology of CH was dyshormonogenesis.

CONCLUSION

The rates of both permanent and transient CH in our study were higher than the comparable worldwide rates. The transient group had low T4 levels, suggesting that iodine contamination should be investigated. The aetiology of CH was also different from that recorded in many other studies.

Polymorphic length of FOXE1 alanine stretch: evidence for genetic susceptibility to thyroid dysgenesis

Familial cases of congenital hypothyroidism from thyroid dysgenesis (TD) (OMIM 218700) occur with a frequency 15-fold higher than by chance, FOXE1 is one of the candidate genes for this genetic predisposition and contains an alanine tract. Our purpose is to assess the influence of length of the alanine tract of FOXE1 on genetic susceptibility to TD. A case-control association study (based on 115 patients affected by TD and 129 controls genotyped by direct sequencing) and transmission disequilibrium testing (TDT) analyses were performed. The transcriptional activities of FOXE1 constructs containing 14 or 16 alanines were also studied. In the case-control association study, the 16/16 and 16/14 genotypes were inversely associated with TD (OR = 0.39, 95%CI = 0.22-0.68, P = 0.0005), strongly suggesting that the presence of 16 alanines in the tract protect against the occurrence of TD. This association was stronger in the subgroup of patients with ectopic thyroid (OR = 0.28, 95%CI = 0.13-0.58, P = 0.00015). The protection was confirmed by the TDT analysis performed in 39 trios (chi(2) = 4.3, P = 0.0374). Alternatively, the presence of the 14/14 genotype is associated with an increase risk of TD (OR = 2.59, 95%CI = 1.56-4.62, P = 0.0005). The expression studies showed that the transcriptional activities of FOXE1 with 16 alanines were significantly higher (1.55-fold) than FOXE1 containing 14 alanines (P < 0.003), while the nuclear localisation of the proteins was not affected. We conclude that FOXE1 through its alanine containing stretch modulates significantly the risk of TD occurrence, enhancing a mechanism linking an alanine containing transcription factor to disease.

TTF-2/FOXE1 gene polymorphisms in Sicilian patients with permanent primary congenital hypothyroidism

Thyroid transcription factor-2 (TTF-2/FOXE1) is a polyalanine domain protein that regulates thyroid embryogenesis, but very few patients with permanent primary congenital hypothyroidism (pCH) harbor germline mutations of this or other transcription factors that are involved in thyroid development that might explain the etiology of pCH. Variations within the polyalanine tract are found in a variety of genes and are often reported in association with malformation syndromes; pCH is frequently associated with thyroid malformations and extra-thyroidal malformations. Therefore, in this study we investigated whether alanine (Ala) length polymorphisms and non-polymorphic mutations of the TTF-2 gene in pCH patients might be involved in the pathogenesis of pCH. The entire coding region of the TTF-2 gene was analyzed in 57 Sicilian patients and 142 healthy controls. We found that the homozygous Ala14 polymorphism (Ala14/14) was less frequent in the pCH group than in the controls. In contrast, significantly more pCH patients than controls harbored the Ala16 polymorphism (Ala16/16 and Ala14/16). However, neither the Ala14/14 nor the Ala16 polymorphism was related to extra-thyroidal malformations. Two of the 57 patients carried Ala11/14 and Ala12/14, and one Ala14/14 patient also had the silent polymorphism 387 C/T (Leu129Leu). Other than known polymorphic variants we found no mutation in the TTF-2 gene. Therefore, this study demonstrates that mutations in the TTF-2 gene are rare in pCH patients and suggests that variations in the length of the Ala-tract could at least partially explain the etiology of pCH but not that of extra-thyroidal malformations.

Genetics, clinical management and natural history of congenital hypothyroidism

Congenital hypothyroidism has an incidence of 1:3000-4000 newborns. In the past, it was a common cause of mental retardation, although newborn screening has improved the prognosis. Several transcription factors are crucial to the early organogenesis of the thyroid, including TITF1, FOXE1, PAX8 and HHEX. Nevertheless, a small minority of humans with congenital hypothyroidism carry mutations in these genes. Long-term follow-up studies show that with appropriate therapy, the mental and physical development of congenital hypothyroidism patients is in the normal range, although somewhat delayed when compared with appropriate controls. Critical issues of treatment include early diagnosis and rapid correction of hypothyroidism by ensuring rapid initiation of treatment and rapid normalization of thyroid-stimulating hormone levels, especially in cases of severe congenital hypothyroidism. There has been recent question of the need to treat premature infants with hypothyroxinemia but no elevation of the thyroid-stimulating hormone concentration. Numerous controlled studies of the short- and long-term effects of thyroid hormone supplementation have not shown a consistent benefit in this group of patients. Future research will investigate further the genetic underpinnings of the condition. There is a worldwide need to prevent congenital hypothyroidism by ensuring adequate dietary iodine and to develop infrastructure to diagnose and treat congenital hypothyroidism in developing countries.