Autoimmune thyroid disease is a condition in which the immune system creates antibodies that damage the thyroid gland. Hashimoto’s thyroiditis and Graves’ disease are the two common types of autoimmune thyroid disease.

Hashimoto’s thyroiditis is the most common cause of underactive thyroid (also known as hypothyroidism) in the United States. It is more common in women. 

The autoantibody in Hashimoto’s thyroiditis is called the thyroid peroxidase antibody (TPO Ab). This disease involves chronic inflammation of the thyroid gland and causes damage to the thyroid cells, which leads to low thyroid hormone levels. This condition usually progresses very slowly over years, and patients typically do not have any symptoms until they develop hypothyroidism. However, in some patients, inflammation can cause enlargement of the thyroid gland (goiter) and, rarely, neck discomfort. 

Patients with hypothyroidism may experience fatigue, weight gain, cold intolerance, constipation, hair loss, dry skin, and abnormal menstrual cycles. Treatment with synthetic thyroid hormone (levothyroxine) is recommended in patients with Hashimoto’s thyroiditis and low thyroid hormone levels. This treatment is inexpensive and very effective in restoring thyroid hormone levels, resulting in improvement of hypothyroid symptoms.  

Grave’s disease

Graves’s disease is the most common cause of overactive thyroid (hyperthyroidism) in the United States, and it is also more common in women. Autoantibodies in Graves’ disease are called thyrotropin receptor antibody (TRAB). 

Patients with active Graves’ disease experience hyperthyroidism symptoms, which may include rapid heartbeat, heat intolerance, frequent bowel movements, anxiety, hand tremors, insomnia, weight loss, and abnormal menstrual cycles. Graves’s disease can also be associated with swelling of the tissue around the eyes. Patients with Graves’ eye disease may experience dryness and redness of their eyes, bulging of the eye, or changes in their vision. In rare cases, patients with Graves’ disease may experience redness and thickening of the skin in front of the shins called pretibial myxedema. Treatment options to control hyperthyroidism due to Graves’ disease are anti-thyroid drugs (methimazole or propylthiouracil), surgery, or radioactive iodine treatment.