There are several causes of hyperthyroidism. Most often, the entire gland is overproducing thyroid hormone. This is called “Graves Disease”. Less commonly, a single nodule is responsible for the excess hormone secretion. The most common underlying cause of hyperthyroidism is Graves' disease, a condition named for an Irish doctor who first described the condition. This condition can be summarized by noting that an enlarged thyroid (enlarged thyroids are called goiters) is producing way too much thyroid hormone. Remember that only a small percentage of goiters produce too much thyroid hormone, the majority of thyroid goiters actually become large because they are not producing enough thyroid hormone.

Graves' disease is classified as an autoimmune disease, a condition caused by the patient's own immune system turning against the patient's own thyroid gland. The hyperthyroidism of Graves' disease, therefore, is caused by antibodies that the patient's immune system makes which attach to specific activating sites on thyroid gland which in turn cause the thyroid to make more hormone.

There are actually three distinct parts of Graves' disease: (1) overactivity of the thyroid gland (hyperthyroidism), (2) inflammation of the tissues around the eyes causing swelling, and (3) thickening of the skin over the lower legs (pretibial myxedema). Most patients with Graves' disease, however, have no obvious eye involvement. Their eyes may feel irritated or they may look like they are staring.

About one out of 20 people with Graves' disease will suffer more severe eye problems, which can include bulging of the eyes, severe inflammation, double vision, or blurred vision. If these serious problems are not recognized and treated, they can permanently damage the eyes and even cause blindness. Thyroid and eye involvement in Graves' disease generally run a parallel course, with eye problems resolving slowly after hyperthyroidism is controlled.
 

Common symptoms and signs of hyperthyroidism:

• Palpitations

• Heat intolerance

• Nervousness

• Insomnia

• Breathlessness

• Increased bowel movements

• Light or absent menstrual periods

• Fatigue

• Fast heart rate

• Trembling hands

• Weight loss

• Muscle weakness

• Warm moist skin

• Hair loss

• Staring gaze

Characteristics of Graves Disease:

• Graves Disease effects women much more often than men (about 8:1 ratio, thus 8 women get Graves Disease for every man that gets it.

• Graves Disease is often called diffuse toxic goiter because the entire thyroid gland is enlarged, usually moderately enlarged, sometimes quite big.

• Graves disease is uncommon over the age of 50 (more common in the 30's and 40's)

• Graves Disease tends to run in families (not known why)

Other Less Common Causes of Hyperthyroidism:

Hyperthyroidism can also be caused by a single nodule within the thyroid instead of the entire thyroid. As outlined in detail on our nodules page, thyroid nodules usually represent benign (non-cancerous) lumps or tumors in the gland. These nodules sometimes produce excessive amounts of thyroid hormones. This condition is called "toxic nodular goiter". The picture on the right is an iodine scan (also simply called a thyroid scan) which shows a normal sized thyroid gland (shaped like a butterfly). This scan is abnormal because a solitary "hot" nodule is located in the right lower lobe. This single nodule is comprised of thyroid cells which have lost their regulatory mechanism which dictates how much hormone to produce. Without this regulatory control, the cells in this nodule produce thyroid hormone at a dramatically increased rate causing the symptoms of hyperthyroidism.

Inflammation of the thyroid gland, called thyroiditis, can lead to the release of excess amounts of thyroid hormones that are normally stored in the gland. In subacute thyroiditis, the painful inflammation of the gland is believed to be caused by a virus, and the hyperthyroidism lasts a few weeks. A more common painless form of thyroiditis occurs in one out of 20 women, a few months after delivering a baby and is, therefore, known as postpartum thyroiditis. Although hyperthyroidism caused by thyroiditis causes the typical symptoms listed on our introduction to hyperthyroidism page, they generally last only a few weeks until the thyroid hormone stored in the gland has been exhausted. For more about thyroiditis see our page on this topic.

Hyperthyroidism can also occur in patients who take excessive doses of any of the available forms of thyroid hormone. This is a particular problem in patients who take forms of thyroid medication that contains T3, which is normally produced in relatively small amounts by the human thyroid gland. Other forms of hyperthyroidism are even rarer.

Nutritional support

Foods that depress the thyroid include broccoli, cabbage, brussels sprouts, cauliflower, kale, spinach, turnips, soy, beans, and mustard greens. Avoid refined foods, dairy products, wheat, caffeine, and alcohol.

• Omega-3 fatty acids are anti-inflammatory and help your immune system function properly.

• Bromelain (250 to 500 mg three times per day between meals) reduces swelling.

• Vitamin C (250 to 500 mg twice a day) supports immune function and decreases inflammation.

• Calcium (1,000 mg per day) and magnesium (200 to 600 mg per day) are cofactors for many metabolic processes.

• Vitamin E (400 IU twice a day) can help protect the heart.

• Coenzyme Q10 (50 mg twice a day) can help protect the heart.