PubMed · 13112440
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A COSTA. 1953. [Hyperthyroidism in cretinism].. https://pubmed.ncbi.nlm.nih.gov/13112440/
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AIMS: To evaluate the prevalence of congenital hypothyroidism (CH) in a screening program performed for the first time in Isfahan, Iran. METHODS: From May 2002 to December 2002, T4 and TSH serum concentrations of 20,000 3- to 7-day-old newborns, born in all 17 hospitals of the city, were measured by radioimmunoassay and immunoradiometric assay, respectively. The newborns with abnormal screening results (TSH >20 mIU/l, T4 <6.5 microg/dl and based on the weight) were re-examined. RESULTS: Of 531 recalled subjects (recall rate 2.6%), 54 were confirmed to be hypothyroid, showing a prevalence of 1:370 for CH. CONCLUSION: Considering the high frequency of CH, the necessity of implementing a routine screening program in the healthcare system of Isfahan Province is emphasized.
UNLABELLED: Early observations emphasized the possible development of hyponatraemia in hypothyroid children and adults, but recently this has been questioned. AIM: To investigate whether hyponatraemia develops in hypothyroid status by examining sodium handling in screening-detected neonates and infants with congenital hypothyroidism (CH). METHODS: Serum thyroid-stimulating hormone (TSH), free thyroxine (FT4), sodium (Na), creatinine (Cr), urinary Na, Cr, fractional sodium excretion rate (FENa) and other chemicals were measured before and after L-thyroxine (LT4) replacement therapy in 32 screening-detected CH neonates (11M, 21F) and 16 age-matched control neonates. RESULTS: No cases of hyponatraemia were found in the 32 CH neonates. Their serum Na concentrations (139.1 +/- 1.5 mmol/L, ranging from 136 to 142 mmol/L, median 139 mmol/L) were not statistically different from those of 16 control neonates (139.3 +/- 1.3 mmol/L, ranging from 137 to 142 mmol/L, median 139 mmol/L). No correlation was found between serum levels of TSH and FT4 and serum Na or FENa. No significant changes were found in serum Na concentrations in hypothyroid neonates two months after LT4 replacement therapy. The serum Na concentration (139.1 +/- 0.3 mmol/L, n = 25) before treatment did not change statistically (138.9 +/- 0.2 mmol/L, n = 25) two months after LT4 replacement therapy. CONCLUSION: As seen in various earlier reports, hyponatraemia can occur in hypothyroid patients, but no causal relationship exists between them. When hyponatraemia is detected in hypothyroid children, it does not seem to be directly related to lack of thyroid hormones and therefore other possible causes should be sought.
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.