Persistent Neonatal Thyrotoxicosis in a Neonate Secondary to a Rare Thyroid-Stimulating Hormone Receptor Activating Mutation: Case Report and Literature Review
ABSTRACT To report the case of a neonate presenting with nonautoimmune thyrotoxicosis and failure to thrive in whom an activating TSHR mutation was suspected.
We describe the clinical and laboratory findings in a neonate who presented with nonautoimmune thyrotoxicosis and failure to thrive, including results of DNA analysis of TSHR, which encodes the thyroid-stimulating hormone receptor (TSHR). Relevant literature is also reviewed.
The proband was born spontaneously at 35 weeks' gestation, and his early neonatal period was remarkable for meconium aspiration, pneumothorax, hepatomegaly with associated elevated transaminases, and direct hyperbilirubinemia. On days 9 and 11 of life, thyroid function studies revealed hyperthyroidism, which remained persistent on day 26 of life. On day 44 of life, the infant was admitted to the hospital. The mother reported he had an increased activity level, disturbed sleep, jitteriness, and exaggerated startle response. Weight was at the third percentile. After additional workup, Lugol's iodine solution, propanolol, and propylthiouracil were prescribed, which led to improvement in thyroid function. No TSHR antibodies were detected in the mother's or patient's sera. Analysis of the patient's DNA revealed a heterozygous T-to-C substitution at amino acid 568 in exon 10 (Ile568Thr), which predicts an isoleucine to threonine conversion in the second extracellular loop of TSHR. The mutation was not identified in the parents' DNA.
A mutation causing constitutive activation of TSHR was confirmed in this patient, a finding that has implications for genetic counseling and consideration of total thyroidectomy or long-term thionamide therapy followed by radioiodide ablation as treatment options. Although rare, TSHR mutations should be considered in an infant presenting with thyrotoxicosis in absence of demonstrable TSHR antibodies in serum.
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ABSTRACT: Up to date, 14 patients with sporadic non-autoimmune hyperthyroidism (SNAH) caused by sporadic germline mutations in the TSH receptor (TSHR) gene have been reported. Despite considerable differences in the activity of hyperthyroidism, all SNAH case reports concluded that the demonstrated constitutive activity explains the phenotype. Recently, linear regression analysis (LRA) of constitutive activity as a function of TSHR expression determined by 125I-bTSH binding or fluorescence activated cell sorting analysis was described as a more reliable way of characterizing the in vitro activity (IVA) of a constitutively activating TSHR mutation. Therefore, we analyzed a possible genotype-phenotype correlation in a systematic review of the case reports and investigated the TSHR mutation's LRA in selected cases. We determined the LRA for all sporadic germline mutations which had not previously been reported. Moreover, we systematically evaluated all case reports of SNAH for evidence of an association of the clinical course (CC) with the IVA of the mutated TSHR. The LRA determined were: M453T (5.2+/-0.8), L512Q (4.5+/-0.7), I568T (25.6+/-6.3), F631L (45.9+/-9.4), T632I (14.5+/-2.7), D633Y (16.4+/-6.4). None of the 10 examined clinical signs showed a significant association with the LRA. Moreover, the comparison of the CC of patients harboring the same mutation (S281N, M453T, I568T, S505N) also showed no relation of the clinical activity with a high LRA. Considering the different diagnostic circumstances, therapeutic strategies and the limitations of a systematic analysis of case reports due to the restricted number of case reports and limited follow-up we found no consistent relation of the TSHR mutation's IVA determined by LRA with the CC of patients with SNAH. This may also be due to the action of genetic, epigenetic, and environmental modifiers.Journal of endocrinological investigation 08/2009; 33(4):228-33. DOI:10.3275/6476 · 1.55 Impact Factor
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ABSTRACT: TSH receptor (TSHR) germline mutations occur as activating mutations in familial non-autoimmune hyperthyroidism (FNAH) or sporadic non-autoimmune hyperthyroidism (SNAH). Up to date 17 constitutively activating TSHR mutations have been reported in 24 families with FNAH. The diagnosis of FNAH should be considered in cases with a positive family history, early onset of hyperthyroidism, goiter, absence of clinical stigmata of autoimmunity and recurrent hyperthyroidism. Moreover, 14 subjects with sporadic non-autoimmune hyperthyroidism and 10 different TSH receptor germline mutations have been reported. The main characteristic of SNAH is a negative family history. Additional consequences of prolonged neonatal hyperthyroidism (mental retardation, speech disturbances and craniosynostosis) have often been reported in SNAH. No genotype-phenotype relationship has been reported in patients with germline TSHR mutations. There is no association of in vitro activities determined by linear regression analysis (LRA) and several clinical indicators of hyperthyroidism activity for SNAH. However, the comparison of the LRA values of sporadic TSHR mutations with LRA values of familial TSHR mutations does show a significantly higher median LRA value for sporadic as compared to familial autosomal dominant hyperthyroidism. This finding is in line with the clinical impression of a more active clinical course in patients with SNAH. However, additional genetic, constitutional or environmental factors are most likely responsible for the phenotypic variations of the disease and the lack of correlation between in vitro activities of the TSHR mutations and the severity of hyperthyroidism.Molecular and Cellular Endocrinology 02/2010; 322(1-2):125-34. DOI:10.1016/j.mce.2010.02.001 · 4.24 Impact Factor
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ABSTRACT: Germline activating mutations of the thyrotropin receptor (TSHR) gene have been considered as the only known cause of sporadic nonautoimmune hyperthyroidism in the pediatric population. Here we describe the long-term follow-up and evaluation of a patient with sporadic nonautoimmune primary hyperthyroidism who was found to have a de novo germline activating mutation of the TSHR gene. The patient was an infant who presented at the age of 10 months in an unconscious state with exsiccation, wet skin, fever, and tachycardia. Nonautoimmune primary hyperthyroidism was diagnosed, and brain magnetic resonance imaging and computed tomography showed also Arnold-Chiari malformation type I. Continuous propylthiouracil treatment resulted in a prolonged clinical cure lasting for 10 years. At the age of 11 years and 5 months the patient underwent subtotal thyroidectomy because of symptoms of trachea compression caused by a progressive multinodular goiter. However, 2 months after surgery, hormonal evaluation indicated recurrent hyperthyroidism and the patient was treated with propylthiouracil during the next 4 years. At the age of 15 years the patient again developed symptoms of trachea compression. Radioiodine treatment resulted in a regression of the recurrent goiter and a permanent cure of hyperthyroidism without relapse during the last 3 years of his follow-up. Sequencing of exon 10 of the TSHR gene showed a de novo heterozygous germline I630L mutation, which has been previously described as activating mutation at somatic level in toxic thyroid nodules. The I630L mutation of the TSHR gene occurs not only at somatic level in toxic thyroid nodules, but also its presence in germline is associated with nonautoimmune primary hyperthyroidism. Our case report demonstrates that in this disorder a continuous growth of the thyroid occurs without any evidence of elevated TSH due to antithyroid drug overdosing. This may justify previous recommendations for early treatment of affected patients with removal of as much thyroid tissue as possible.Thyroid: official journal of the American Thyroid Association 02/2010; 20(3):327-32. DOI:10.1089/thy.2009.0182 · 3.84 Impact Factor