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Hashimoto thyroiditis

Hashimoto thyroiditis (also known as lymphocytic thyroiditis 1 or chronic autoimmune thyroiditis 2) is a subtype of autoimmune thyroiditis. It is one of the most common of all thyroid disorders. 

Epidemiology

Typically affects middle aged females (30-50 year age group with a F:M ratio of 10-15:1). 

Clinical presentation

Patients usually present with hypothyroidism +/- goitre. However a very small proportion of cases (~5%) can present with hyperthyroidism (hashithyrotoxicosis). There is often a gradual painless enlargement of the thyroid gland during the initially phase with atrophy and fibrosis later on in the course.

Pathology

There is autoimmunity to the thyroid gland which bears both humoral and cell mediated features. This is followed by lymphocytic infiltration of the thyroid gland with lymphoid follicles replacing thyroid follicles. This may affect the thyroid gland in either a diffuse or focal manner. Cell populations include 

  • lymphocytic aggregates
  • transformed follicular cells (Askanazy/oxyphilic/Hurthle cells)

Later stages show added fibrosis.

Serological markers
  • antithyroglobulin antibodies: found in ~70% of cases 2
  • thyroid peroxidase antibodies (TPO): found in 90-95% of cases 2
Associations

Radiographic features

Ultrasound

It is difficult to reliably sonographically differentiate Hashimoto thyroiditis from other thyroid pathology. Ultrasound features can be variable depending of the severity and phase of disease 1,5:

  • diffusely enlarged thyroid gland with a heterogeneous echotexture is a common sonographic presentation 6
  • presence of hypoechoic micronodules (1-6 mm) with a surrounding echogenic septations is also considered to have a relatively high positive predictive value 3,4
  • colour Doppler study usually shows normal or decreased flow, but occasionally there might be hypervascularity similar to thyroid inferno
  • prominent reactive cervical nodes may be present, especially in level VI, but they have normal morphologic features
  • patients are at higher risk for papillary thyroid carcinoma, so a discrete nodule should be considered for biopsy

In some situations, large nodules may be present: see nodular Hashimoto thyroiditis 10.

Scintigraphy
Radioactive iodine 
  • early stages: may show increased uptake 
  • late stages: single or multiple areas of reduced uptake (cold spots). 

History and etymology

It was first described in 1912 by Hikaru Hashimoto, Japanense physician (1881-1934) while working in Germany in 1912.

Differential diagnosis

For ultrasound appearances consider:

See also


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