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.
SourceAvailable from: Anca M Avram[Show abstract] [Hide abstract]
ABSTRACT: Background:Activating mutations of the TSH receptor (TSHR) are rare, with few reported cases of long-term follow-up.Case:We present a follow-up report on a patient with neonatal thyrotoxicosis known to have a rare activating mutation of the TSHR, a heterozygous substitution in exon 10 (p.Ile568Thr). Initial treatment included total thyroidectomy at age 2 years, resulting in iatrogenic hypothyroidism and hypoparathyroidism. The patient was treated with levothyroxine replacement to maintain TSH levels within normal range, as well as calcitriol and calcium carbonate to treat postsurgical hypoparathyroidism. However, 4 years later, while euthyroid, he developed a palpable 1-cm midline neck mass.Methods and Results:Functional imaging with 123-I thyroid scan demonstrated active thyroid tissue within the thyroglossal duct remnant and in the tracheoesophageal groove. Surgical removal of the neck mass revealed cytologically bland thyroid follicular cells.Conclusion:These findings suggest that even after total thyroidectomy, patients with TSHR-activating mutations are at risk to develop significant quantities of functional thyroid tissue related to the hypertrophy of residual foci in the thyroid bed and in the thyroglossal duct remnant. These residual foci may enlarge and secrete thyroid hormones autonomously, decreasing the patient's levothyroxine requirement. Surveillance with serial physical examination and biochemical monitoring is recommended; suspicious findings can be further evaluated with functional thyroid imaging (99-m technetium or radioiodine 123-I thyroid scans) to adequately identify residual foci of thyroid tissue, which may require further treatment with surgical excision or radioablation.The Journal of Clinical Endocrinology and Metabolism 12/2012; 98(2). DOI:10.1210/jc.2012-3146 · 6.31 Impact Factor
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ABSTRACT: All cases of familial thyrotoxicosis with absence of evidence of autoimmunity and all children with persistent isolated neonatal hyperthyroidism should be evaluated for familial non-autoimmune autosomal dominant hyperthyroidism (FNAH) or persistent sporadic non-autoimmune hyperthyroidism (PSNAH). First, all index patients should be analysed for the presence/absence of a thyroid-stimulating hormone (TSH) receptor (TSHR) germline mutation, and if they display a TSHR germline mutation, all other family members including asymptomatic and euthyroid family members should also be analysed. A functional characterization of all new TSHR mutations is necessary. Appropriate ablative therapy is recommended to avoid relapses of hyperthyroidism and its consequences, especially in children. Therefore, in children the diagnosis of FNAH or PSNAH needs to be established as early as possible in the presence of the clinical hallmarks of the disease.10/2012; 1(3):142-147. DOI:10.1159/000342982
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ABSTRACT: Neonatal hyperthyroidism is a rare condition caused either by transplacental passage of thyroid-stimulating immunoglobulins from a mother with Graves' disease or by activating mutations of the thyrotropin receptors and α-subunit of G-protein. The clinical features may vary. We report a case of neonatal thyrotoxicosis in an infant born to a mother with Graves' disease, who presented with cardiorespiratory failure and persistent pulmonary hypertension (PPHN). PPHN resolved with specific antithyroid treatment and extracorporeal membrane oxygenation was not required.Case Reports 05/2012; 2012. DOI:10.1136/bcr.02.2012.5939