| What is hyperthyroidism? |
Your thyroid is a butterfly-shaped gland located at the base of your neck, just below your Adam's apple. Although it weighs less than an ounce, the thyroid gland has an enormous impact on your health. Every aspect of your metabolism, from your heart rate to how quickly you burn calories, is regulated by thyroid hormones.
As long as your thyroid produces the right amount of these hormones, your metabolism functions normally. But sometimes your thyroid gland produces too much of the hormone thyroxine — a condition known as hyperthyroidism (overactive thyroid disease). This can accelerate your body's metabolism — sometimes by as much as 60 percent to 100 percent — causing sudden weight loss, a rapid or irregular heartbeat and nervousness or irritability.
Women are more likely than men to have hyperthyroidism. Although the condition usually occurs in young or middle-aged adults, it can also affect adolescents and older adults.
No one treatment is right for every person with hyperthyroidism. Most commonly, radioactive iodine is used to slow the production of thyroid hormones, but sometimes antithyroid drugs may be used. In rare cases, part of the gland may be surgically removed. Although hyperthyroidism can be fatal if it's ignored, most people respond well once the condition is diagnosed and treated.
| Signs and symptoms |
Hyperthyroidism can mimic other health problems, which may make it difficult to diagnose. It can also cause a wide variety of signs and symptoms, including:
- Sudden weight loss, even when your appetite and food intake remain normal or increase
- Rapid or irregular heartbeat (arrhythmia) or pounding of your heart
- Nervousness, irritability, tremor
- Sweating
- Changes in menstrual patterns
- Increased sensitivity to heat
- Changes in bowel patterns, especially more frequent bowel movements
- An enlarged thyroid (goiter), which may appear as a swelling at the base of your neck
- Fatigue, muscle weakness
- Difficulty sleeping
Sometimes an uncommon problem called Graves' ophthalmopathy may affect your eyes. In this disorder, your eyeball protrudes beyond its normal protective orbit when tissues and muscles behind your eye swell, pushing the eyeball forward. This can cause the front surface of your eyeball to become very dry. Other signs and symptoms of Graves' ophthalmopathy include:
- Red or swollen eyes
- Widening of the space between your eyelids
- Excessive tearing or discomfort in one or both eyes
- Light sensitivity, blurry or double vision, inflammation or reduced eye movement
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| Causes |
Your thyroid gland produces two main hormones, thyroxine and triiodothyronine. They maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate and help regulate the production of protein. Your thyroid gland also produces calcitonin, a hormone that regulates the amount of calcium in your blood.
The rate at which these hormones are released is controlled by your pituitary gland and your hypothalamus — an area at the base of your brain that acts as a thermostat for your whole system. Here's how the process works:
The hypothalamus signals your pituitary gland to make a hormone called thyroid-stimulating hormone (TSH). Your pituitary gland then releases TSH — the amount depends on how much thyroxine and triiodothyronine are in your blood. Finally, your thyroid gland regulates its production of hormones based on the amount of TSH it receives.
Normally, your thyroid releases the right amount of hormones, but sometimes it produces too much thyroxine. This may occur for a number of reasons, including:
- Graves' disease. Most hyperthyroidism is caused by Graves' disease, an autoimmune disease
in which antibodies produced by your immune system stimulate the thyroid to produce too much
thyroxine. Normally, your immune system uses antibodies to help protect against viruses, bacteria and
other foreign substances that invade your body. In Graves' disease, antibodies mistakenly attack your
thyroid gland and occasionally the tissue behind your eyes and the skin of your lower legs. Scientists
aren't sure exactly what causes Graves' disease, although several factors — including a genetic
predisposition — are likely involved. Sometimes a viral infection or stress also can trigger Graves'
disease.
- Hyperfunctioning thyroid nodules (toxic adenoma, toxic multinodular goiter, Plummer's
disease). This form of hyperthyroidism occurs when one or more adenomas of your thyroid produce
too much thyroxine. An adenoma is a part of the gland that has walled itself off from the rest of the
gland, forming noncancerous (benign) lumps that may cause an enlargement of the thyroid. Not all
adenomas produce thyroxine, and researchers aren't sure what causes some to begin producing the
hormone.
- Thyroiditis. Sometimes your thyroid gland can become inflamed for unknown reasons. The inflammation can cause excess thyroid hormone stored in the gland to leak into your bloodstream. One rare type of thyroiditis, known as subacute thyroiditis, causes severe pain in the thyroid gland. Other types are painless and may sometimes occur after pregnancy (postpartum thyroiditis).
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| When to seek medical advice |
If you experience unexplained weight loss, a rapid heartbeat, unusual sweating, swelling at the base of your neck or other signs and symptoms associated with hyperthyroidism, see your doctor. It's important to completely describe the changes you've observed, because many signs and symptoms of hyperthyroidism may be associated with a number of other conditions.
If you've been treated for hyperthyroidism or currently are being treated, see your doctor regularly so he or she can monitor your condition.
| Screening and diagnosis |
Hyperthyroidism is diagnosed using your medical history, a physical exam and blood tests. During the exam your doctor may try to detect a slight tremor in your fingers when they're extended, overactive reflexes, eye changes, and warm, moist skin. He or she will also examine your thyroid gland as you swallow.
The diagnosis can be confirmed with blood tests that measure the levels of thyroxine and TSH in your blood. High levels of thyroxine and low or nonexistent amounts of TSH indicate an overactive thyroid. The amount of TSH is important because it's the hormone that signals your thyroid gland to produce more thyroxine. These tests are particularly necessary for older adults, who may not have classic symptoms of hyperthyroidism.
If blood tests indicate hyperthyroidism, your doctor may recommend a radioactive iodine uptake test or thyroid scan. This can help determine the exact cause of your overactive thyroid and will aid in planning treatment.
For the uptake test, you'll be given a small amount of radioactive iodine to take orally. Over a period of time, the iodine will collect in your thyroid gland because your thyroid uses iodine to manufacture hormones. You'll be checked after 2, 6 or 24 hours — or sometimes after all three time periods — to determine how much iodine your thyroid gland has absorbed.
A high uptake of radioiodine indicates your thyroid gland is producing too much thyroxine. The most likely cause is either Graves' disease or hyperfunctioning nodules. If you have hyperthyroidism but your radioiodine uptake is low, you may have thyroiditis.
During the thyroid scan, you'll have a radioactive isotope injected into the vein on the inside of your elbow. You then lie on a table with your head stretched backward while a special camera produces an image of your thyroid on a computer screen. The time needed for the procedure may vary, depending on how long it takes the isotope to reach your thyroid gland.
A thyroid scan is painless, but you may have some neck discomfort. You'll also be exposed to a slight amount of radiation with both a thyroid scan and a radioactive iodine uptake test.
| Complications |
Some of the most serious complications of hyperthyroidism involve the heart. These include a rapid heart rate, atrial fibrillation and congestive heart failure — a condition in which your heart becomes too weak to circulate enough blood to meet the needs of your body.
Untreated hyperthyroidism can also lead to weak, brittle bones (osteoporosis). The strength of your bones depends, in part, on the amount of calcium and other minerals they contain. Too much thyroid hormone interferes with your body's ability to incorporate calcium into your bones. Hyperthyroidism often affects your bones before you have any other symptoms of the disorder.
People with Graves' ophthalmopathy develop eye problems, including bulging, red or swollen eyes, sensitivity to light and blurring or double vision. In rare cases, Graves' disease also affects the skin, causing redness and swelling on the shins and feet.
If you have hyperthyroidism, you're also at risk of thyrotoxic crisis — a sudden intensification of your symptoms, leading to a fever, a rapid pulse and even delirium. If this occurs, seek immediate medical care.
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| Treatment |
Several treatments for hyperthyroidism exist. The best approach for you depends on your age, physical condition and the severity of your disorder:
- Radioactive iodine. This is the most common treatment used in the United States. Taken by
mouth, radioactive iodine is absorbed by your thyroid gland, where it causes the gland to shrink and
symptoms to subside, usually within 2 to 3 months. Because this treatment causes thyroid activity to
slow considerably, you may eventually need to take a medication every day to replace thyroxine.
- Antithyroid medications. These medications gradually reduce symptoms of hyperthyroidism by
preventing your thyroid gland from producing excess amounts of hormones. They include propylthiouracil
and methimazole (Tapazole). Symptoms usually improve in 6 to 8 weeks, but treatment with antithyroid
medications typically continues for a year or more. For some people, this clears up the problem
permanently, but many other people experience a relapse.
- Surgery (thyroidectomy). If you can't tolerate antithyroid drugs and don't want to have
radioactive iodine therapy, you may be a candidate for thyroid surgery, although this is an option in
only a few cases. For most people, other treatments are preferred.
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In a thyroidectomy, your doctor removes most of your thyroid gland. Risks of this surgery include
damage to your vocal cords and parathyroid glands — four tiny glands located on the back of your
thyroid gland that help control the level of calcium in your blood. In addition, you'll need
lifelong treatment with levothyroxine (Synthroid) to supply your body with normal amounts of
thyroid hormone. If your parathyroid glands also are removed, you'll need medication to keep your
blood calcium levels normal.
If you're taking Synthroid, or have taken it in the past, you may have heard that it didn't go through the standard Food and Drug Administration (FDA) approval process. As a result, the FDA required Synthroid's manufacturers to submit a new drug application, and in July 2002, the drug was approved as "safe and effective."
If Graves' disease affects your eyes, mild symptoms can be managed by avoiding wind and bright lights and using artificial tears and lubricating gels. If your symptoms are more severe, your doctor may recommend treatment with corticosteroids, such as prednisone, to reduce swelling behind your eyeball. In some cases, one of the surgical procedures listed below may be an option:
- Orbital decompression surgery. In this surgery, your doctor removes the bone between your
eye socket and your sinuses — the air spaces next to the eye socket. When the procedure is successful,
it improves vision and provides room for your eyes to return to their normal position. But there is a
risk of complications, including double vision that persists or appears following surgery.
- Eye muscle surgery. Sometimes scar tissue from Graves' ophthalmopathy can cause one or more eye muscles to be too short. This pulls your eyes out of alignment, leading to double vision. Eye muscle surgery may help correct double vision by cutting the affected muscle from the eyeball and reattaching it farther back. The goal is to achieve single vision when you read and look straight ahead. In some cases, more than one operation may be necessary.
| Self Care |
Once you begin treatment, symptoms of hyperthyroidism should subside and you should start feeling much better. The following suggestions also may help:
- Ask your doctor about supplementing your diet. If you've lost a great deal of weight or
experienced muscle wasting, you may benefit from adding extra calories and protein to your diet. Your
doctor or a nutritionist can help you plan an appropriate diet.
- Maintain an adequate intake of calcium. Because hyperthyroidism may contribute to thinning bones, it's important to get enough calcium every day to help prevent osteoporosis. Aim for a total of 1,500 milligrams daily, either from food you eat or from supplements or both.
If you have Graves' ophthalmopathy, the following suggestions may help soothe your eyes or skin:
- Apply cool compresses to your eyes. The extra moisture may provide relief.
- Wear sunglasses. When your eyes protrude, they're more vulnerable to ultraviolet rays and
more sensitive to sunlight. Wearing sunglasses helps protect them.
- Use lubricating eyedrops. Eyedrops may help relieve dryness and scratchiness.
- Elevate the head of your bed. Keeping your head higher than the rest of your body reduces
blood flow to your head and may help relieve the pressure on your eyes.
- Try over-the-counter creams for swollen skin. Over-the-counter creams containing hydrocortisone or triamcinolone may help relieve red, swollen skin on your shins and feet. For help finding these creams, talk to your pharmacist.