Congenital Hypothyroidism
Congenital hypothyroidism remains the leading cause of preventable mental impairment worldwide. It is most often caused by iodine deficiency (endemic cretinism) or thyroid dysgenesis but can be caused by any defect in thyroid hormone production, regulati
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Cecilia A. Larson
Abstract
Congenital hypothyroidism remains the leading cause of preventable mental impairment worldwide. It is most often caused by iodine deficiency (endemic cretinism) or thyroid dysgenesis but can be caused by any defect in thyroid hormone production, regulation, or action. Because congenital hypothyroidism is common and newborns initially exhibit few specific signs or symptoms of the disorder, most developed countries offer universal newborn thyroid screening. With early identification and treatment of affected newborns, neurologic sequelae are minimized, and development in most adequately treated cases is normal. Keywords
Congenital hypothyroidism • Iodine deficiency • Thyroid dysgenesis • Thyroid screening • Thyroxine-stimulating hormone
Introduction Congenital hypothyroidism remains the leading cause of preventable mental impairment worldwide. It is most often caused by iodine deficiency (endemic cretinism) or thyroid dysgenesis but can be caused by any defect in thyroid hormone production, regulation, or action (see Table 15.1). Because congenital hypothyroidism is common and newborns initially exhibit few specific signs or symptoms of the disorder, most developed C.A. Larson, M.D. (*) Beth Israel Deaconess Hospital Needham, Harvard Medical School,148 Chestnut Street, Needham, MA 02492, USA e-mail: [email protected]
countries offer universal newborn thyroid screening. With early identification and treatment of affected newborns, neurologic sequelae are minimized, and development in most adequately treated cases is normal. Recognition of iodine deficiency and attempts to eliminate the problem have been ongoing for decades, yet there remain significant areas of deficiency. Ongoing surveillance for iodine status is important as dietary deficiency tends to recur in certain populations and regions. While iodine deficiency can cause thyroid disorders in all ages, the fetus and newborn are at special risk for consequences of insufficient iodine due to the critical thyroxine-dependent intervals of neurodevelopment. For this reason, surveillance and treatments
S. Radovick and M.H. MacGillivray (eds.), Pediatric Endocrinology: A Practical Clinical Guide, Second Edition, Contemporary Endocrinology, DOI 10.1007/978-1-60761-395-4_15, © Springer Science+Business Media New York 2013
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C.A. Larson
262 Table 15.1 Causes of congenital hypothyroidism (CH) Primary hypothyroidism Thyroid dysgenesis Athyreotic Ectopic Hypothyreotic (ex hemithyroid) Thyroid hormone dysgenesis—goitrous enzyme defect Iodine deficiency Iodine transporter defect Peroxidase defect Thyroglobulin synthetic defect Peripheral thyroid hormone inactivation Tumor deiodinase activity Iodotyrosine deiodinase defect TSH resistance (normal or hypoplastic gland) Transient hypothyroidism TSH receptor (TR-b)mutations Gsa gene mutations Maternal antithyroid medications Maternal antibodies-Maternal thyrotropin receptor-blocking antibody (TRB-Ab) Iodine Idiopathic Central hypothyroidism Hypothalamic Pituitary Pituitary maldevelo
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