Aspectos genéticos do hipotireoidismo congênito

Incidence of congenital hypothyroidism in the city of Uberaba/Minas Gerais and etiological evaluation of the affected subjects

OBJECTIVE

The objective of this study was to determine the incidence and etiology of congenital hypothyroidism (CH) in Uberaba, MG.

SUBJECTS AND METHODS

From 2001 to 2010, by reviewing patient files from a public reference outpatient unit. The screening program covered 88% of live-born children.

RESULTS

CH was diagnosed in 16 children, representing an incidence of 1:2,017 live-born children screened. The etiological evaluation was done in 15 children and revealed seven cases of thyroid dysgenesis, seven of dyshormonogenesis, and one case of transient hypothyroidism. One child moved away from the state before etiological investigation was carried out.

CONCLUSION

We concluded that both the incidence of CH and of dyshormonogenesis as the main causes of CH were increased in the investigated region, but molecular studies are necessary for a better definition of etiology.

The R450H mutation and D727E polymorphism of the thyrotropin receptor gene in a Chinese child with congenital hypothyroidism

BACKGROUND

Congenital hypothyroidism (CH) is the most prevalent congenital endocrine disorder. The molecular cause of CH in the majority of newborns is unknown. The aim of this study was to investigate the mutation of thyrotropin receptor (TSHR) gene in Chinese children with congenital hypothyroidism (CH). and the hereditary characteristic.

METHODS

Eighteen Chinese children with CH were enrolled for molecular analysis of the TSHR gene and 105 normal controls were evaluated. The exons 1-9, and 10 of TSHR gene were detected by PCR-SSCP (single-stranded conformation polymorphism) and sequenced.

RESULTS

A slower and a faster mobility SSCP shift showed in a 12-year old child with hypoplasic gland. Sequencing of TSHR gene revealed a homozygous mutation (CGC --> CAC, Arg450His) and a polymorphism (GAC --> GAG, Asp727Glu). The controls revealed no variants. The 12 relatives of the proband were enrolled and investigated. Six relatives, including his mother and father, were heterozygous for R450H mutation and D727E polymorphism of the TSHR gene. Thyroid hormone levels were normal except for circulating TSH (5.96-6.92 mU/L) level slightly elevated in six heterozygous family members.

CONCLUSIONS

Homozygous mutation R450H of the TSHR gene led to CH. Heterozygous mutation R450H was the cause of subclinical hypothyroidism.

Etiology of congenital hypothyroidism using thyroglobulin and ultrasound combination

Methods currently employed to establish the etiology of congenital hypothyroidism include thyroid ultrasound and scintigraphic exams. Thyroglobulin is a protein almost exclusively secreted by thyroid tissue and indirectly reflects the amount of follicular cells. Even though thyroglobulin is easy to measure, it has been not frequently used because of discordant results to distinguish mainly athyreosis and ectopy (dysgenesis). Knowing the differences in inheritance and prognosis of thyroid dysgenesis and dyshormonogenesis, it is important to define the etiology of CH, combining tools that are easy, fast and available in most medical centers. Our objective was to evaluate and compare color Doppler ultrasound and serum thyroglobulin with radionuclide scan to define the etiology of congenital hypothyroidism. We evaluated 38 children above 3 years-old off-treatment that performed serum thyroglobulin by immunofluorometric assay, color Doppler ultrasound and radionuclide study. On color Doppler ultrasound, 11 patients had athyreosis, 5 ectopic glands, being 1 associated to hemiagenesis. Twenty one had topic thyroid (3 goiters, 10 normal, 8 hypoplastic). Hemiagenesis and cystic lesion were not revealed by radionuclide scan. We observed substantial agreement between color Doppler ultrasound and radionuclide scan (kappa=0.745, p<0.0001). Serum thyroglobulin in athyreosis ranged from <1.0 to 18.7 micro g/L. Patients with ectopic glands showed wider thyroglobulin range (4.5 to 123 micro g/L, median 28.4 micro g/L). Only one patient showed thyroglobulin deficiency. By using color Doppler ultrasound and serum thyroglobulin levels as valuable combined tools, we established the etiology of congenital hypothyroidism limiting excessive and harmful exams in children, like radionuclide scan.