What tests diagnose Hashimoto's thyroiditis?
To diagnose Hashimoto's thyroiditis, a physician should assess symptoms and complaints commonly seen in hypothyroidism, carefully examine the neck to look for enlargement of the thyroid gland, and take a detailed history of family members. Blood tests are essential to diagnose Hashimoto's thyroiditis. Specific blood tests determine the level of thyroid function.
During the early stage of thyroiditis, the levels of thyroid hormones (T3 and T4) may be normal. With chronic hypothyroidism, the thyroid hormone levels fall, and the level of thyroid-stimulating hormone (TSH) becomes high. The most useful assay for determining thyroid status is measurement of TSH in the blood. As mentioned earlier, TSH is secreted by the pituitary gland. As the level of thyroid hormone falls, the pituitary gland responds by releasing more thyroid-stimulating hormone (TSH). The increase in TSH can actually precede the fall of thyroid hormone to low levels by months or years, so the first sign of hypothyroidism may be an elevated TSH level even when levels of thyroid hormones are normal.
The blood work mentioned above confirms the diagnosis of hypothyroidism, but does not point to an underlying cause. The combination of the patient's clinical history, antibody screening (as mentioned above), and a thyroid scan can help diagnose the precise underlying thyroid problem. If a pituitary or hypothalamic cause is suspected, MRI of the brain and other studies may be warranted. These investigations should be made on a case-by-case basis.
Illustration of the Pituitary Gland
The blood tests also usually include an analysis of antibodies (anti-thyroperoxidase antibodies) to aid diagnosis. If the anti-TPO antibodies are elevated at all, the diagnosis is made. Early on in the course of the disease, however, the patient may have negative antibodies.
If the gland is large, or there are symptoms of esophageal compression, an ultrasound may be performed to see if the gland is compressing either the esophagus (the food tube) or the trachea (the airway).