Hormones secreted by the thyroid gland control metabolism, or the speed at which the body converts food into energy. Metabolism is directly linked to the amount of hormones that circulate in the bloodstream. If, for some reason, the thyroid gland secretes too much of these hormones, the body’s metabolism kicks into high gear, causing a pounding heart, sweating, trembling, and weight loss.
Normally, the thyroid gets its production orders through another chemical called thyroid-stimulating hormone (TSH), released by the pituitary gland in the brain. But in Graves’ disease, a malfunction in the body’s immune system releases abnormal antibodies that act like TSH. Spurred by these false signals to produce, the thyroid’s hormone factories work overtime and overproduce.
Exactly why the immune system begins to produce these troublesome antibodies isn’t clear. Heredity and other characteristics seem to play a role. Studies show, for example, that if one identical twin contracts Graves’ disease, there is a 20% likelihood that the other twin will get it too. Also, women are more likely than men to develop the disease. And smokers who develop Graves’ disease are more prone toeye problems than nonsmokers with the disease. No single gene causes Graves’ disease. It is thought to be triggered by both genetics and environmental factors.