From the Guidelines
If the thyroid appears to have had thyroiditis at some point, recommended labs to order include:
- Thyroid-stimulating hormone (TSH) level to assess current thyroid function, as it has a high sensitivity (98%) and specificity (92%) in confirming suspected thyroid disease 1
- Free thyroxine (FT4) and free triiodothyronine (FT3) levels to evaluate the thyroid hormone levels, which can help differentiate between subclinical and overt thyroid dysfunction 1
- Thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) tests to check for autoimmune thyroiditis, as Hashimoto thyroiditis is a common cause of hypothyroidism 1
- Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) to assess for ongoing inflammation, which can be associated with thyroiditis 1
Additionally, consider ordering a thyroid ultrasound to evaluate the thyroid gland's structure and check for any nodules or abnormalities.
It's also important to assess for any symptoms of hypothyroidism or hyperthyroidism and adjust the treatment plan accordingly. If hypothyroidism is suspected, levothyroxine (Synthroid) may be prescribed, starting with a low dose of 25-50 mcg daily and adjusting as needed based on TSH levels, as it is the principal treatment for hypothyroidism 1. If hyperthyroidism is suspected, beta blockers such as propranolol (Inderal) may be prescribed to manage symptoms, starting with a dose of 20-40 mg daily, although treatment is typically not recommended for patients with TSH levels between 0.1 and 0.45 mIU/L or when thyroiditis is the cause 1.
From the Research
Laboratory Tests for Thyroiditis
If the thyroid gland shows evidence of previous thyroiditis, the following laboratory tests are indicated:
- Thyroid-stimulating hormone (TSH) test to assess the functional status of the thyroid 2
- Free thyroxine (FT4) and free triiodothyronine (FT3) tests to evaluate the levels of thyroid hormones 2, 3
- Thyroid peroxidase antibodies (TPO-Ab) test to diagnose Hashimoto's thyroiditis 4, 2
- Thyroglobulin (Tg) and thyroglobulin antibodies (Tg-Ab) tests to evaluate the presence of thyroiditis and to monitor for changes in thyroid function 2
- TSH receptor antibodies (TRAb) test to diagnose Graves' disease 2, 3
Additional Tests
Depending on the clinical presentation and the results of the initial tests, additional tests may be ordered, such as:
- Thyroid ultrasound to assess the size and structure of the thyroid gland 5
- Radionuclide scanning to evaluate the uptake of iodine by the thyroid gland 5
- Fine needle aspiration biopsy to evaluate thyroid nodules 5
Interpretation of Test Results
It is essential to consider the clinical context when interpreting the results of these tests, as thyroid function may appear abnormal in the absence of actual thyroid dysfunction during pregnancy and in critical illness 2. Additionally, the results of these tests should be interpreted in conjunction with the patient's symptoms, medical history, and physical examination findings 4, 6, 3, 5.