From the Guidelines
Diagnosing Hashimoto's thyroiditis typically involves a combination of blood tests, clinical evaluation, and sometimes imaging, with the primary diagnostic tests including measuring thyroid stimulating hormone (TSH) and free T4 levels, as well as checking for thyroid antibodies, particularly thyroid peroxidase antibodies (TPO) and thyroglobulin antibodies (TgAb) 1. The most recent and highest quality study, published in 2015 in the Annals of Internal Medicine, recommends the serum TSH test as the primary screening test for thyroid dysfunction, with multiple tests done over a 3- to 6-month interval to confirm or rule out abnormal findings 1. Some key points to consider in the diagnosis of Hashimoto's thyroiditis include:
- The most common cause of hypothyroidism in the United States is chronic autoimmune (Hashimoto) thyroiditis, with risk factors for an elevated TSH level including female sex, advancing age, white race, type 1 diabetes, Down syndrome, family history of thyroid disease, goiter, previous hyperthyroidism, and external-beam radiation in the head and neck area 1.
- The USPSTF found no direct evidence that treatment of thyroid dysfunction based on risk level alters final health outcomes, highlighting the need for long-term randomized, blinded, controlled trials of screening for thyroid dysfunction to provide the most direct evidence on any potential benefits of this widespread practice 1.
- Symptoms that might prompt testing for Hashimoto's thyroiditis include fatigue, weight gain, cold intolerance, constipation, dry skin, and depression, with early diagnosis important as Hashimoto's often leads to hypothyroidism, which requires lifelong thyroid hormone replacement therapy, typically with levothyroxine starting at doses of 1.6 mcg/kg body weight daily, adjusted based on TSH levels every 6-8 weeks until stable 1. It is essential to prioritize the single most recent and highest quality study, which in this case is the 2015 study published in the Annals of Internal Medicine, to ensure that the diagnosis and treatment of Hashimoto's thyroiditis are based on the most up-to-date and reliable evidence 1.
From the Research
Diagnosis of Hashimoto's Thyroiditis
To diagnose Hashimoto's thyroiditis, several factors and tests are considered, including:
- Thyroid-specific antibodies such as thyroglobulin antibodies (TgAb) and thyroid peroxidase antibodies (TPOAb) 2, 3, 4, 5
- Thyroid-stimulating hormone (TSH) levels, which can indicate hypothyroidism 6, 4
- Free triiodothyronine (fT3) and free thyroxine (fT4) levels to assess thyroid function 6
- Thyroid ultrasound to evaluate thyroid volume and structure 6, 5
- Presence of symptoms such as hypothyroidism, thyrotoxicosis, or euthyroidism 4
Diagnostic Criteria
The diagnosis of Hashimoto's thyroiditis can be based on a combination of the following criteria:
- Elevated TPOAb and/or TgAb levels 2, 3, 4, 5
- Typical hypoechogenicity of the thyroid in high-resolution sonography 6
- Low pertechnetate uptake in thyroid scintigraphy 6
- Presence of lymphocytic infiltration of the thyroid gland 5
Scoring System
A comprehensive scoring system has been proposed to diagnose Hashimoto's thyroiditis, which includes:
- TPOAb levels
- TgAb levels
- Thyroid vascularity This scoring system has a sensitivity of 45.5% and a specificity of 89.0% with a cutoff of 1.7 5
Clinical Presentation
Hashimoto's thyroiditis can present with various clinical manifestations, including:
- Hypothyroidism
- Thyrotoxicosis
- Euthyroidism
- Symptom burden, which is associated with elevated TgAb levels 2