Hyperthyroidism

Hyperthyroidism develops when the thyroid gland makes too much thyroid hormone.

Thyroid hormone controls your metabolism, how your body turns food into energy, and influences your heart rate, digestion, muscle and bone strength and cholesterol levels. When you have too much thyroid hormone, all of your body's functions speed up.

Cause

Graves' disease is the most common cause of hyperthyroidism. Graves' disease causes the thyroid gland to make too much thyroid hormone. Graves' disease, like many thyroid problems, often runs in families.

Other common causes include:

• Thyroid nodules - Thyroid nodules are abnormal growths in the thyroid gland that make too much thyroid hormone.
• Thyroiditis - Thyroiditis occurs when your body makes antibodies that damage your thyroid gland. You can get thyroiditis from a viral or bacterial infection. At first, thyroiditis may cause your thyroid levels to rise as hormone leaks out from the damaged gland. Later, levels may be low until the gland repairs itself.

Uncommon causes of hyperthyroidism include tumors, eating foods or taking medications that contain large amounts of iodine.

Symptoms

You may have hyperthyroidism if you:

• Feel nervous, moody, weak or tired.
• Have hand tremors, a fast or irregular heartbeat or trouble breathing; even when you are resting.
• Sweat a lot and have warm, red skin that may be itchy.
• Have frequent and sometimes loose bowel movements.
• Have fine, soft hair that is falling out.
• Lose weight even though you are eating normally or more than usual.

In addition, some women have irregular menstrual cycles or stop having periods altogether, and some men may develop enlarge breasts.

The symptoms of hyperthyroidism are not the same for everyone. Your symptoms depend on how much hormone your thyroid gland is making, how long you have had the condition and your age. If you are older, it's easy to mistakenly dismiss your symptoms as normal signs of aging.

What increases your risk

You are more likely to have hyperthyroidism if:

• You are female, women are more likely to develop hyperthyroidism than men.
• You have a family history of thyroid problems. People who have close relatives with Graves' disease or other thyroid problems are more likely to develop hyperthyroidism.
• You have an autoimmune disease, such as Addison's disease type one diabetes.
• You smoke cigarettes, people who smoke are more likely to have Graves' disease and are more likely to have Graves' ophthalmopathy.
• You have recently been through a stressful time such as a divorce or the loss of your job.