(HealthDay News) -- Graves' disease occurs when the body's immune system causes the thyroid gland to produce more of a certain hormone than the body can use.

Symptoms may include an enlarged thyroid, insomnia, nervousness, a sensitivity to heat, and uncontrolled hand movement. Some people with the disease have swollen eyes.

The National Women's Health Information Center says the following factors may contribute to Graves' disease:

• Having a family history (genetic predisposition).
• Being a woman and producing female hormones.
• Experiencing extreme emotional stress or significant trauma may help trigger the disease in people who are prone to it.
• Being pregnant, which affects the thyroid.
• Having an infection.