Hashimoto thyroiditis

Last revised by Dr Jeremy Jones on 20 Sep 2021

Hashimoto thyroiditis, also known as lymphocytic thyroiditis or chronic autoimmune thyroiditis, is a subtype of autoimmune thyroiditis. It is one of the most common thyroid disorders. 

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

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

The Hashitoxicosis phase, if present, usually only lasts 1-2 months. Although rare cases last much longer 16.

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 superadded fibrosis.

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

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

  • diffusely enlarged thyroid gland with a heterogeneous echotexture is a common sonographic presentation (especially initial phase) 6
  • the presence of hypoechoic micronodules (1-6 mm) with surrounding echogenic septations is also considered to have a relatively high positive predictive value 3,4; this appearance may be described as pseudonodular or a giraffe pattern.
  • color Doppler study usually shows normal or decreased flow, but occasionally there might be hypervascularity similar to a thyroid inferno
    • the hypervascularity does not reflect thyrotoxicosis, indeed it appears to be more common in hypothyroid Hashimoto patients 11!
  • 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, which may be referred to as nodular Hashimoto thyroiditis 10.

  • early stages: may show increased uptake 
  • late stages: single or multiple areas of reduced uptake (cold spots)
  • diffuse high uptake throughout the thyroid is consistent with chronic thyroiditis (or a normal variant) 14,15
  • superimposed focal high uptake should raise concern for a thyroid nodule including the possibility of carcinoma

It was first described in 1912 by Hakaru Hashimoto (1881-1934), a Japanese physician 7 while working in Germany; in his original description, he called it 'struma lymphomatosa' 13.

For ultrasound appearances consider:

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Cases and figures

  • Figure 1: pathology cut slice
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  • Figure 2: histology
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  • Case 1
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  • Case 2
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  • Case 3: pseudonodular appearance
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  • Case 4
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  • Case 5: with thyroid Inferno
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