Causes and Symptoms
No one knows exactly what causes the body's immune system to turn against its own healthy cells in Graves' disease or any other autoimmune condition. One thing we do know is that the condition definitely has a tendency to run in families.
Because autoimmune problems are much more prevalent in women, some experts think hormones may be involved in the disease process, too. But as with most other autoimmune conditions, no one knows for sure how reproductive hormones might promote autoimmunity.
Some experts suspect that environmental factors are at play as well. One study in 2005 found that cigarette smoking was linked to the incidence of Graves' in women — the more cigarettes women smoked, the greater their likelihood of developing Graves'.
Other studies have suggested that emotionally stressful events may play a role in triggering Graves' disease. Still other possible culprits include viruses, infections, pollution, and bacteria. But again, these are theories, and the exact cause of any autoimmune disease remains a mystery. Most people believe that it's a combination of genetics and environmental factors that cause Graves'.
It is possible to have no symptoms of hyperthyroidism and still have Graves' disease. Most people who have this condition, which is called euthyroid Graves' disease, have thyroid eye disease. Some become hyperthyroid, but others never do.
In mild cases, Graves' disease sometimes produces no symptoms at all, especially in the early stages. But in most people, though not all, Graves' disease tends to lead to symptoms of hyperthyroidism. Eventually, you may begin to notice that you're losing weight for no apparent reason despite an increase in appetite. Your heart may be beating faster, and you may feel nervous and on edge.
You may also be sweating more often and sensitive to warm temperatures that others find comfortable. Women may notice that their periods are lighter or that they disappear altogether.
As your body's metabolic rate increases, you may have more frequent bowel movements, possibly even diarrhea. You may also notice hair loss and rapid growth of your fingernails. Your skin may be more delicate and thin, and you may notice trembling in your hands. At night, you may be plagued by insomnia. By the end of the day, you are frequently exhausted.
Too much thyroid hormone also takes a toll on your moods. Besides feeling anxious and jittery, you may be irritable, quarrelsome, and sad. Your moods may swing wildly for no apparent reason, and you may fluctuate between bouts of depression and mania. In some people, Graves' disease can resemble panic disorder.
Unfortunately, the antibodies involved in Graves' disease attack the eyes, too. As a result, Graves' disease affects the eyes in a way that other forms of hyperthyroidism does not, although people who have advanced hyperthyroidism of any type will appear to have a wide-eyed, startled appearance. This unusual stare occurs when the muscles that raise the upper eyelid are overstimulated by the excess thyroid hormone, causing the skin of the upper eyelid to be slightly lifted, exposing the white above the top of the iris. About half of people with Graves' will go on to develop a separate condition called thyroid eye disease, or infiltrative ophthalmology. The condition is also sometimes called exophthalmos. With this condition, patients develop a distinct bulging of the eyeball. This protrusion occurs as a result of swelling in the muscles around the eyes, which pushes the eyeball forward. Some people may have difficulty closing their eyes completely, which leads to redness and irritation of the eyeball. You will find a more thorough discussion of thyroid eye disease later in this chapter.