Hashimoto's Thyroiditis is an autoimmune disease. In Hashimoto's, the immune system is attacking the thyroid gland. Specific lab testing will present with immune cells in the thyroid. Immune cells should not be in the thyroid gland. These immune cells attack the thyroid gland and cause damage to it and cause the thyroid to become enlarged. The damage to the thyroid will continue until the thyroid is treated with medication.
In addition, Hashimoto's causes a low TSH level and a high level of antibodies.
Also, the free T-3 and T-4 levels will be low.
( In measuring the TSH level, the higher the number, the lower the TSH level is) For example, a TSH level of 5.0 is considered low. In comparison, a high TSH level, the lower the number will be, such as 1.0.
There are five stages in Hashimoto's Thyroiditis. If the thyroid is not treated with medication,the immune cells in the thyroid will cause a progression of the damage to the thyroid. In stage five, the damage to the thyroid is extreme. Eventually, the thyroid will be irreversibly damaged.
The thyroid will stop functioning.
Unfortunately, most patients with Hashimoto's will fail to be diagnosed until stage 3.
Hashimoto's "may" cause the TSH level to go from a hypothyroid state to a hyperthyroid state. If this occurs, the TSH level will always go back to a hypothyroid state in Hashimoto's.
A "normal" TSH level for one person, may not be normal for another individual.
A patients symptoms are a good indicator of an abnormal TSH level etc....
Hypothyroidism generally causes fatigue, weight gain, brain fog, and in some people it will cause a lot of bodily pain.
Of course, everyone is different.