Goiter

BASICS

DESCRIPTION

A goiter is an enlarged thyroid gland (also known as thyromegaly). A simple or colloid goiter is not associated with thyroid dysfunction, autoimmune thyroid disease, or neoplastic process. Thyroid nodules are present in some goiters.

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 prevalence 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.

ETIOLOGY

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

RISK FACTORS

  • Family history
  • Female sex
  • Autoimmune disease such as type 1 diabetes
  • Tobacco smoke
  • Radiation
  • Iodine deficiency or excess
  • Certain drugs (e.g., lithium, tyrosine kinase inhibitors, some anticonvulsants)
  • Certain chromosomal differences (Down syndrome, Turner syndrome)

Genetics

  • Mutations in the following genes can result in a simple goiter:
    • Thyroid peroxidase
    • Sodium iodide symporter
    • Thyroglobulin
    • Thyroid-stimulating hormone (TSH) receptor
  • Germline mutations in DICER1 cause familial multinodular goiter.
  • Mutations associated with the development of thyroid cancer:
    • Thyroid transcription factor-1 (TITF-1/NKX2.1): MNG and papillary thyroid carcinoma
    • RET proto-oncogene: medullary thyroid cancer
    • BRAF: papillary thyroid cancer
    • RAS and PAX8–PPAR-γ: follicular thyroid cancer

GENERAL PREVENTION

Iodine administration reduces endemic goiter incidence.

PATHOPHYSIOLOGY

  • In autoimmune thyroid disease, thyromegaly results from thyrotropin receptor stimulation, either by increased TSH in the setting of hypothyroidism or TSH-receptor stimulating antibodies.
  • Thyroid enlargement can also develop due to inflammation, as seen in thyroiditis, or infiltration.
  • The pathogenesis of euthyroid simple goiter remains unclear.

COMMONLY ASSOCIATED CONDITIONS

  • Autoimmune thyroid disease is associated with certain genetic disorders and other autoimmune diseases.
    • Down syndrome and Turner syndrome
    • Type 1 diabetes and celiac disease
      • Autoimmune polyglandular syndrome type 2 (APS-2): Addison disease plus Hashimoto thyroiditis and/or type 1 diabetes
  • Pendred syndrome: congenital sensorineural deafness and goiter due to mutation in pendrin, which transports iodide into the thyroid follicular lumen

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