Hashimoto thyroiditis (HT) is a chronic inflammation of the thyroid gland initially described over a century ago but of still incompletely defined etiopathogenesis. It is now considered the most common autoimmune disease, the most common endocrine disorder, as well as the most common cause of hypothyroidism.
The diagnostic criteria for Hashimoto’s thyroiditis (also known as chronic lymphocytic thyroiditis or autoimmune thyroiditis) are based on clinical, laboratory, and imaging findings. Here’s a concise summary of the key diagnostic components:
1. Clinical Features
Symptoms of hypothyroidism (often develop gradually):
- Fatigue
- Cold intolerance
- Weight gain
- Constipation
- Depression
- Menstrual irregularities
- Goiter (diffusely enlarged, firm, and non-tender thyroid)
- Family history of autoimmune disease
2. Laboratory Findings
Thyroid Function Tests:
- TSH: Elevated (most sensitive marker of hypothyroidism)
- Free T4: Low or low-normal
Thyroid Autoantibodies:
- Anti-thyroid peroxidase antibodies (TPOAb): Present in >90% of patients
- Anti-thyroglobulin antibodies (TgAb): Present in ~60-80% of cases
Note: Positive TPOAb is the most important serologic marker for Hashimoto’s.
3. Ultrasound of the Thyroid
- Hypoechogenicity (dark appearance)
- Heterogeneous echotexture
- Pseudonodules or micronodules
- Increased vascularity (sometimes)
Ultrasound can support the diagnosis and help differentiate from other thyroid diseases.
4. Fine Needle Aspiration (FNA) Biopsy
Usually not required unless nodules are suspicious for malignancy.
Histology (if performed) shows:
- Lymphocytic infiltration
- Germinal centers
- Hurthle cell (oncocytic) changes
- Fibrosis (in later stages)
5. Associated Conditions
- Other autoimmune diseases (e.g., Type 1 diabetes, vitiligo, celiac disease)
- Down syndrome and Turner syndrome (higher risk)
Diagnostic Summary
Hashimoto’s thyroiditis is diagnosed when there is:
- Clinical or subclinical hypothyroidism and
- Positive TPO antibodies ± TgAb and/or
- Typical ultrasound features
In some cases, diagnosis is made in euthyroid individuals with positive antibodies and characteristic ultrasound findings, considered an early stage of the disease.
References:
- Weetman AP. An update on the pathogenesis of Hashimoto’s thyroiditis. J Endocrinol Invest. 2021 May;44(5):883-890. [Medline]
- Ralli M, Angeletti D, Fiore M, D’Aguanno V, Lambiase A, Artico M, de Vincentiis M, Greco A. Hashimoto’s thyroiditis: An update on pathogenic mechanisms, diagnostic protocols, therapeutic strategies, and potential malignant transformation. Autoimmun Rev. 2020 Oct;19(10):102649. [Medline]
Created Jul 29, 2025
