From the Guidelines
For autoimmune thyroiditis, I recommend ordering thyroid function tests including thyroid-stimulating hormone (TSH), free thyroxine (free T4), and free triiodothyronine (free T3) to assess thyroid function status, as well as thyroid autoantibody tests, specifically thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb), which are typically elevated in autoimmune thyroiditis, as suggested by 1. These tests are crucial because autoimmune thyroiditis (Hashimoto's thyroiditis) is the most common cause of hypothyroidism in iodine-sufficient regions, and early detection allows for appropriate management of thyroid hormone levels before significant symptoms develop. Some key points to consider when ordering lab work for autoimmune thyroiditis include:
- The serum TSH test is the primary screening test for thyroid dysfunction, as stated in 1.
- Multiple tests should be done over a 3- to 6-month interval to confirm or rule out abnormal findings, as recommended in 1.
- Follow-up testing of serum T4 levels in persons with persistently abnormal TSH levels can differentiate between subclinical (normal T4 levels) and “overt” (abnormal T4 levels) thyroid dysfunction, as noted in 1.
- Complete blood count (CBC) should be included to check for anemia or other blood abnormalities that may accompany autoimmune conditions.
- Comprehensive metabolic panel (CMP) helps evaluate overall health status and organ function.
- In some cases, thyroid ultrasound may be warranted to assess thyroid structure and identify nodules or characteristic heterogeneous appearance. Regular monitoring of thyroid function is necessary as the disease can progress from euthyroid to hypothyroid state over time, as indicated in 1 and 1. It is also important to note that the presence of thyroid autoantibodies (antithyroid peroxidase [TPO] and antithyroglobulin [TG]) identifies patients at increased risk for thyroid autoimmunity, as stated in 1. Therefore, a comprehensive approach to lab work for autoimmune thyroiditis should include a combination of these tests to ensure accurate diagnosis and effective management of the condition.
From the FDA Drug Label
In adult patients with primary hypothyroidism, monitor serum TSH levels after an interval of 6 to 8 weeks after any change in dosage. In patients on a stable and appropriate replacement dosage, evaluate clinical and biochemical response every 6 to 12 months and whenever there is a change in the patient’s clinical status In patients with hypothyroidism, assess the adequacy of replacement therapy by measuring both serum TSH and total or free-T4.
For autoimmune thyroiditis, the lab work to order includes:
- Serum TSH levels to assess the adequacy of replacement therapy
- Total or free-T4 levels to evaluate the clinical and biochemical response to treatment These lab tests should be monitored:
- Every 6 to 8 weeks after any change in dosage
- Every 6 to 12 months in patients on a stable and appropriate replacement dosage
- Whenever there is a change in the patient’s clinical status 2
From the Research
Lab Work for Autoimmune Thyroiditis
The following lab work is typically ordered for autoimmune thyroiditis:
- Complete blood cell count (CBC) with differential 3
- Complete metabolic profile (CMP) 3
- Thyroid function tests, including:
- Thyroid antibodies, including:
- High-sensitivity C-reactive protein (hs-CRP) 3
Rationale for Lab Work
These lab tests are used to diagnose and monitor autoimmune thyroiditis, as well as to assess the severity of the disease. The presence of thyroid antibodies, such as TPO and TGA, can indicate autoimmune thyroiditis 4, 5. Thyroid function tests, including TSH, T4, and T3, can help assess the level of thyroid hormone production and identify any abnormalities 3, 4. The hs-CRP test can help assess inflammation, which is often present in autoimmune thyroiditis 3.