American Medical Association Family Medical Guide - American Medical Association [616]
Hyperthyroidism
Hyperthyroidism (also called Graves’ disease) is a disorder in which the thyroid gland is overactive and produces excessive amounts of thyroid hormones. Activity of the thyroid gland is normally controlled by secretion of thyrotropin (also called thyroid-stimulating hormone, or TSH) by the pituitary gland. In hyperthyroidism, the control mechanism malfunctions—although the pituitary reduces its production of thyrotropin, the thyroid gland continues to produce large quantities of thyroid hormones. The resulting high levels of thyroid hormones in the blood generally speed up all of the chemical reactions in the body, causing both physical and psychological symptoms.
Hyperthyroidism can result from an autoimmune disorder in which the immune system mistakenly attacks the thyroid gland, causing it to become overactive. Thyroid nodules (see page 903) are another possible cause of hyperthyroidism. Thyroid nodules are noncancerous cysts in the thyroid gland that are filled with functioning thyroid tissue. The nodules produce thyroid hormones in addition to the hormones produced by the thyroid gland itself.
Older people and people who have high blood pressure (see page 574) or atherosclerosis (see page 557) have an increased risk of hyperthyroidism. Hyperthyroidism occurs more frequently in women than in men.
Symptoms
Although the symptoms of hyperthyroidism vary from person to person, most people experience a combination of several of the following symptoms:
• Nervousness and anxiety
• Irritability
• Difficulty sleeping
• Trembling of the body and hands
• Weakness
• Fatigue
• Confusion
• Decreased sensitivity to cold
• Increased sensitivity to heat
• Sweating
• Irregular heartbeat, rapid heartbeat, or palpitations
• High blood pressure
• Shortness of breath after mild exertion
• Frequent bowel movements (sometimes with diarrhea)
• Increased appetite combined with weight loss
• Light menstrual periods or absence of periods
• Prominent swelling in the front of the neck (called goiter)
• Puffiness around the eyes
• Bulging eyes
• Intense, constant stare
• Sensitivity to light
• Abnormally smooth skin
• Nail changes
In some people, high blood pressure or a rapid, irregular heartbeat may put additional strain on the heart and circulation, causing chest pain called angina (see page 559), arrhythmias (see page 580), or heart failure (see page 570).
Diagnosis
If you have symptoms of hyperthyroidism, your doctor will ask about your symptoms and examine you. He or she will probably arrange for you to have a blood test that measures the level of thyrotropin and indicates either high or low activity of the thyroid gland. The doctor may also recommend a blood test to measure the level of thyroid hormones in the blood. To confirm the diagnosis, blood tests may be done to check for antibodies (proteins the immune system mistakenly produces to attack the thyroid gland); the presence of antithyroid antibodies indicates an autoimmune response. Once hyperthyroidism is diagnosed, your doctor may arrange for a thyroid scan to determine whether part or all of your thyroid gland is affected. A thyroid scan is a type of radionuclide scan (see page 114), in which you swallow a small amount of radioactive iodine and lie under a special camera that detects the radiation in the thyroid gland.
Treatment
Before beginning treatment for hyperthyroidism, your doctor will probably prescribe blood pressure medications called beta blockers to slow your heart rate, to control trembling, and to reduce anxiety. Although these drugs will quickly relieve your symptoms, they will not affect the level of