Goiter

Basics

DESCRIPTION

A goiter is an enlarged thyroid gland (also known as thyromegaly). A simple or colloid goiter is one that is not associated with thyroid dysfunction, autoimmune thyroid disease, or a neoplastic process. Goiters can be classified by size and by the presence or absence of nodules.

EPIDEMIOLOGY

  • The incidence of goiter in school-age children ranges from 1.9% to 6.8%.
  • The prevalence of goiter in the United States is 3–7%, although it is much higher in regions of iodine deficiency (15.8% globally).
  • Prevalence in childhood peaks during adolescence with females more affected than males.
  • Thyroid cancer is a rare cause of pediatric goiter and makes up 0.5–1.5% of all malignancies in children and adolescents.

RISK-FACTORS

  • Family history
  • Female gender
  • Autoimmune disease such as type 1 diabetes
  • Tobacco smoke
  • Radiation
  • Iodine deficiency
  • Excessive maternal ingestion of iodine during pregnancy can lead to congenital goiter.

GENETICS

  • Mutations in the following genes can result in a simple goiter:
    • Thyroid peroxidase
    • Sodium iodide symporter
    • Thyroglobulin
    • Thyroid-stimulating hormone (TSH) receptor
  • Multinodular goiter (MNG) loci have been identified on chromosome 14q and on chromosome Xp22 and 3q26.
  • Germline mutations in DICER1 (chromosome 14q31) have been found in familial MNG-1.
  • Germline mutation in thyroid transcription factor-1 (TITF-1/NKX2.1) has been found in patients with papillary thyroid carcinoma and a history of MNG.
  • Thyroid cancers are usually sporadic. Medullary carcinoma can be familial (autosomal dominant), as part of multiple endocrine neoplasia (MEN) type 2A and 2B, or as isolated malignancy. The genetic mutation is in the RET gene.

GENERAL-PREVENTION

Iodine administration reduces the incidence of endemic goiter.

PATHOPHYSIOLOGY

  • Stimulation of the thyrotropin receptor (either by TSH or TSH-receptor antibodies) results in thyromegaly.
  • Thyroid enlargement can also develop due to inflammation, as seen in thyroiditis, or infiltration.
  • The pathogenesis of euthyroid simple goiter remains unclear.

ETIOLOGY

  • The most common cause of pediatric goiter in the United States is chronic lymphocytic thyroiditis (Hashimoto thyroiditis).
  • Genetic etiologies as listed above

ASSOCIATED-CONDITIONS

  • Pendred syndrome (autosomal recessive): congenital sensorineural deafness and goiter due to a mutation in pendrin which transports iodide into the thyroid follicular lumen
  • MEN2A: medullary thyroid cancer, pheochromocytoma, parathyroid adenoma
  • MEN2B: medullary thyroid cancer, pheochromocytoma, mucosal neuromas, marfanoid habitus
  • Autoimmune polyglandular syndrome (APS): Consider other autoimmune diseases such as type 1 diabetes, Addison disease, and pernicious anemia.

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