PubMed · 1159607
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A G Klein, T P Foley. 1975. Letter: Screening for hypothyroidism.. https://doi.org/10.1016/s0022-3476(75)80882-1
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OBJECTIVE: We wished to ascertain whether mutations in the TSH receptor (TSHR) gene were present in two siblings with congenital hypothyroidism with no parental consanguinity. DESIGN: The pituitary-thyroid axis and thyroid gland morphology were investigated in both affected siblings and their parents. The TSHR gene was analysed in each subject. MEASUREMENTS: Basal thyroid function together with circulating thyroglobulin levels were measured in each subject. In addition, a TRH stimulation test was undertaken in each parent. All family members underwent thyroid ultrasonography. The TSHR gene was amplified from genomic DNA using the polymerase chain reaction and receptor mutations were identified by sequence analysis. RESULTS: Two siblings were diagnosed with severe congenital hypothyroidism (total T4 19-21 nmol/l, TSH 160-230 mU/l on neonatal screening). Although radioiodine scanning showed no tracer uptake and ultrasound imaging in both individuals failed to demonstrate thyroid tissue, suggesting complete athyreosis, circulating thyroglobulin levels were measurable. The thyroid status of the parents was discordant: in the father, baseline thyroid function (FT4 13 pmol/l, TSH 4 mU/l), the peak TSH level after TRH stimulation (30 mU/l) were normal and he exhibited an appropriate rise in circulating thyroid hormones in response to the elevated TSH; in contrast, in the mother, baseline thyroid function was abnormal (FT4 10 pmol/l, TSH 15 mU/l), the TSH response to TRH was exaggerated (110 mU/l), with no subsequent rise in circulating thyroid hormones. An eutopic, slightly hypoplastic thyroid gland was visualized on ultrasonography in the mother and her thyroid antibody status was negative. Both children were compound heterozygotes for missense (alanine to threonine at codon 553, A553T) and premature stop (tryptophan at codon 546, W546X) mutations in the fourth transmembrane domain of the TSH receptor. The mother and father were heterozygous for W546X and A553T mutations, respectively. Each mutation is known to abolish the function or cellular surface expression of the TSH receptor. CONCLUSIONS: Inactivating mutations in the TSH receptor can be associated with severe TSH resistance presenting as congenital hypothyroidism with apparent athyreosis. Our observations also suggest that heterozygosity for an inactivating TSHR mutation may be associated with compensated hypothyroidism and thyroid hypoplasia.
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OBJECTIVE: Following elimination of iodine deficiency in Iran, the program of screening for congenital hypothyroidism (CH) was established in 1998. The descriptive findings of the study are reported here. METHODS: From February 1998 to June 2001, cord blood spot samples from 8 hospitals and a rural birth center in Tehran and Damavand were collected and tested for TSH measurement using a two-site IRMA method. TSH values > or = 20 microU/mL were recalled. The diagnosis of CH was confirmed using age adjusted reference values for serum TSH and T4 levels. RESULTS: Of 20107 screened neonates, 256 had cord TSH values > or = 20 microU/mL (recall rate: 1.3%) and 22 showed hypothyroidism (1:914 live births). History of maternal ingestion of drugs and dietary goitrogens were negative and minimal, respectively. 15 out of 21 CH neonates had parental consanguinity. The odds ratio of CH occurrence in blood-related to non-related marriages was 6.9 (CI=1.82-25.87). Thyroid dysgenesis occurred in 10 neonates; 1:2011 births. Urinary iodine excretion was between 12-22 (n=3) and 40-42.5 (n=5) microg/dL in 10 eutopic neonates (2 not assessed). CONCLUSION: Parental consanguinity and iodine excess could be the causative factors for the high incidence of CH.