Hashimoto thyroiditis

Last revised by Han Xin Lau on 29 Apr 2024

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 and causes of hypothyroidism 17.

Hashimoto thyroiditis affects ~2% of all women (F:M = 10-15:1), most commonly in the 30-50 year range 17,22.

The diagnosis of Hashimoto's thyroiditis is usually based on the combination of clinical features, serology results, and ultrasound findings 17,22. However, cytology/histology remains the gold standard for diagnosis 22.

The clinical presentation is variable and some may be asymptomatic 17,22. Patients can present with a painless goiter +/- symptoms of hypothyroidism 17,22. There is often a gradual painless enlargement of the thyroid gland during the initial phase with atrophy and fibrosis later on in the course. Very rarely, patients can present with a painful thyroid (known as painful Hashimoto thyroiditis) 19.

A small proportion of cases (~5%) can present with hyperthyroidism (also known as Hashitoxicosis), which usually only lasts 1-2 months 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.

  • TSH: high 17

  • free T4: low 17

  • antithyroglobulin antibodies: found in ~70% of cases 2,17

  • thyroid peroxidase antibodies (TPO): found in 90-95% of cases 2,17

N.B. Serological markers can be variable 17.

Ultrasound features can be variable depending on the severity and phase of disease as well as differentiate diffuse from nodular Hashimoto thyroiditis.

Prominent reactive cervical nodes may be present, especially in level VI, but they have normal morphologic features ref.

  • typically an enlarged thyroid gland with a hypoechoic, diffusely heterogeneous echotexture with hypoechoic micronodules (1-7 mm) with surrounding echogenic septation 3,4,17,22

    • micronodular 17, pseudonodular, or giraffe pattern has a positive predictive value of 95% 17

    • hypoechogenicity is associated with hypothyroidism 17

    • thyroid gland may be small/atrophic in chronic cases ref

  • color Doppler study usually shows slight diffuse hypervascularity, but occasionally there might be marked hypervascularity similar to a thyroid inferno 17,22

    • marked hypervascularity does not reflect thyrotoxicosis; indeed it appears to be more common in hypothyroid Hashimoto patients 11

  • also known as focal Hashimoto or lymphocytic thyroiditis

  • nodules are larger at 15-18 mm (6-30 mm) diameter 17,22

  • more commonly occurs in the setting of diffuse Hashimoto thyroiditis (~75%, range 55-85%) than normal thyroid parenchyma 22

  • no typical sonographic appearance 17

    • most commonly a hypoechoic nodule with a thin hypoechoic halo and no calcification 17,22

    • nodules can also be echogenic or isoechoic 17,22

    • may be solitary or multiple 17

    • cystic components and calcification are uncommon 17,22

    • margins may be smooth or irregular 17,22

    • variable vascularity 17,22

  • early stages: may show increased uptake ref

  • late stages: single or multiple areas of reduced uptake (cold spots) ref

  • 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 ref

Life-long oral administration of L-thyroxine (T4) is often required ref.

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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