In most cases, an initial diagnosis requires checking the blood levels of T3, T4, and thyroid stimulating hormone (TSH).
T3 and T4 are the hormones produced by the thyroid gland. TSH is a hormone produced by the brain that acts on the thyroid gland to induce hormone production.
In cases of hypothyroidism, the levels of free T3 and T4 are generally low. The TSH levels are high. It means that despite stimulation, the thyroid gland itself is not able to produce hormones.
As Hashimoto’s thyroiditis is autoimmune, its diagnosis can involve the detection of antibodies as well. These mainly include anti thyroid peroxidase (TPO) antibodies and anti-thyroglobulin antibodies.
However, in the initial stages of thyroid disease, these hormonal changes might not be the same. The thyroid hormone levels can be higher than normal if tested at an early stage of the disease.