From the Guidelines
Hashimoto's thyroiditis can cause abnormal T3 and T4 levels, but the pattern of abnormality can vary throughout the disease course. In early stages, thyroid hormone levels (T3 and T4) may be normal while TSH begins to rise, as noted in the context of screening for thyroid dysfunction 1. As the disease progresses and the thyroid gland becomes more damaged, T3 and T4 levels typically decrease, resulting in hypothyroidism. The pattern usually shows low free T4 and free T3 with elevated TSH. However, some patients may experience temporary hyperthyroidism (elevated T3 and T4) during periods of thyroid inflammation when stored hormones are released, known as "Hashitoxicosis."
Some key points to consider in the management of Hashimoto's thyroiditis include:
- The serum TSH test is the primary screening test for thyroid dysfunction, and multiple tests should be done over a 3- to 6-month interval to confirm or rule out abnormal findings 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 1.
- The principal treatment for hypothyroidism is oral T4 monotherapy (levothyroxine sodium), with dosing adjusted based on subsequent lab results and symptom improvement.
- Regular monitoring of thyroid function tests (TSH, free T4, and sometimes free T3) is essential for patients with Hashimoto's, as hormone levels can fluctuate over time.
From the Research
Hashimoto's Disease and Thyroid Hormone Levels
- Hashimoto's disease may present with abnormal T3 and T4 levels, as seen in a case report where a patient had elevated free T3 levels, normal free T4 levels, and low TSH levels 2.
- In some cases, patients with Hashimoto's disease may experience malabsorption of thyroid hormones, including T3 and T4, due to the presence of anti-T3 and anti-T4 antibodies 3.
- The clinical presentation of Hashimoto's thyroiditis can include thyrotoxicosis, euthyroidism, and hypothyroidism, with varying levels of T3 and T4 4.
- Vitamin D supplementation has been shown to have a potential effect on thyroid autoantibodies and thyroid profile in Hashimoto's thyroiditis, although no significant changes were observed in T3 and T4 hormone levels 5.
- Levothyroxine sodium oral solution has been used to normalize thyroid function in patients with Hashimoto's disease, particularly in those with malabsorption issues due to gastrointestinal disorders 6.
Thyroid Hormone Levels in Hashimoto's Disease
- Elevated T3 levels have been reported in some cases of Hashimoto's disease, often with suppressed TSH levels 2.
- Normal or decreased T4 levels have been observed in patients with Hashimoto's disease, depending on the stage and severity of the disease 2, 3.
- TSH levels can be low, normal, or elevated in Hashimoto's disease, depending on the clinical presentation and treatment 2, 6, 4.
- Anti-T3 and anti-T4 antibodies can interfere with thyroid hormone absorption and measurement, leading to abnormal T3 and T4 levels 3.