New tests, new drugs and new understanding can help you detect the problem and stop it
America's first lady described it better than any doctor could have. "My thyroid gland just went wacko," Barbara Bush explained last year. She'd just been diagnosed as having Graves' disease, a potentially serious condition in which the thyroid pumps out excess amounts of hormone.
Barbara Bush is certainly in good company. She's one of about seven million Americans known to have a thyroid disorder. Another three million have a problem thyroid but don't know it. In fact, thyroid disorders occur much more often than even many doctors realize. They're particularly common among middle-aged and older women, where they often go unrecognized or are often mistaken for something else.
The butterfly-shaped thyroid gland is in the neck, its two wings wrapped around the windpipe just below the Adam's apple. The thyroid weighs less than an ounce, but it can have an enormous impact on your health.
Think of it as the body's regulator. It does the job by releasing two hormones, the more important of which is the iodine-containing hormone thyroxine. The hormones help regulate heartbeat, body temperature, how quickly a person burns calories, how swiftly food moves through the digestive tract, and more.
Normally, the thyroid doles out just the right amount of hormone to keep these processes humming smoothly. But it may turn overactive and pump out too much hormone, or underactive and pump out too little. Either way, the abnormal hormone level can profoundly affect the body's metabolism.
IN THE SLOW LANE
Probably five million Americans have an underactive thyroid, a condition called hypothyroidism, the most common thyroid problem. In most cases, it's caused by an autoimmune reaction---no one knows exactly why but the immune system makes antibodies that mistakenly attack and damage thyroid cells, progressively reducing the thyroid's hormone output.
Hypothyroidism causes all the body's processes to slow down. Yet many people with underactive thyroids don't know it. The American Thyroid Association estimates that half of all people with hypothyroidism haven't been diagnosed, or they've been misdiagnosed.
For unknown reasons, hypothyroidism overwhelmingly afflicts women, especially those between 35 and 60. They develop the condition four times more often than men. Some experts recommend a thyroid examination as part of every gynecological checkup.
In a thyroid exam, the doctor carefully feels the thyroid gland to see if it's abnormally enlarged. An enlarged thyroid, known as a goiter, can occur in both hyper- and hypothyroidism. If you do have a goiter, your doctor can then order blood tests to determine the cause of the thyroid problem.
Compared to other diseases, hypothyroidism can be difficult to recognize, especially in older people. Unless doctors suspect a thyroid problem, they may mistake the varied symptoms for psychosomatic complaints or attribute them to normal female aging.
The woman herself is often fooled, too. Hypothyroidism usually comes on gradually, over several months or even years. The early clues may be scarcely noticeable, or you may attribute them to other causes. You may feel tired most of the time, have weak or aching muscles, feel cold, be constipated or gain weight even though you're eating less.
As the thyroid continues losing steam, you may notice that your face looks puffier or your hair looks coarse. Your nails may be brittle, and your skin may seem drier than usual. Or you may notice that a necklace that once hung loosely now feels like a choker. Your thyroid has grown bigger, developing into a goiter, as it attempts to manufacture more hormone.
(In past decades, people often developed goiters because they lived in parts of the country where food and water lacked iodine, which the thyroid must have to make its hormones. Now that iodine is added to salt, iodine deficiency is rarely a cause of hypothyroidism.)
Other physical symptoms of hypothyroidism include cramps, dizziness, a deepening voice and abnormal menstrual periods---quite heavy or absent. Hypothyroidism may also increase blood cholesterol levels. Some experts now recommend testing people with high cholesterol levels to see if their thyroids are a contributing factor.
And then there are the effects that hypothyroidism can have on mental functioning: inability to concentrate, forgetfulness and depression. These mental symptoms have led to tragic cases where hypothyroidism was misdiagnosed as senility, madness or psychosis, says Steven R. Gambert, M.D., chairman of geriatrics and gerontology at New York Medical College.
"Signs and symptoms of hypothyroidism are more easily recognized in a 20-year-old patient," Dr. Gambert says. "Unfortunately, in a 70-year-old, these same signs and symptoms are too often dismissed as accompaniments of ordinary aging." He recommends that doctors determine if a failing thyroid could be the real cause of their older patients' problems.
Fortunately, doctors can easily diagnose hypothyroidism with new and sensitive blood tests. And once the problem is diagnosed, treatment is as simple as a once-a-day tablet. The tablet contains thyroid hormone to compensate for the thyroid's diminished output. Like a fresh rewind for a run-down clock, the replacement therapy primes a sluggish metabolism.
ALL REVVED UP
Picture yourself sitting in a car that's idling quietly in the driveway---until you press the accelerator to the floor. About two million Americans are similarly revved up. Their thyroids pump out excess hormones, which push their metabolism into overdrive. This is hyperthyroidism, and it may produce diverse symptoms: frequent loose stools, heightened sensitivity to heat, excessive sweating, weight loss, fatigue, muscle weakness, nervousness, irritability, insomnia and hand tremors. Another symptom---a rapidly pounding heart when you're at rest---can be especially serious. It can intensify chest pain in people with heart disease and even cause a heart attack.
Mrs. Bush lost 18 pounds in two months without dieting---a classic sign of hyperthyroidism. She also developed eye problems. In her words, they started getting "big, puffy, horrible." That was the tip- off to Graves' disease, named after a nineteenth-century Irish physician. It's the most common type of hyperthyroidism, accounting for half of all cases. And it can be fatal if left untreated.
Graves' disease affects mainly women, especially those aged 30 to 55. Like hypothyroidism, it's an autoimmune disease. In Graves', some antibodies attack thyroid cells, stimulating them to produce excess amounts of hormones. Other antibodies may attack the muscles and other tissues around the eye. As these tissues become inflamed, they push against the eyeball and cause the symptoms that bothered Mrs. Bush: bulging of the eyeball, painful pressure and persistent double vision. The pressure can lead to blindness if it's not corrected.
Treating Graves' disease may require treating both the thyroid gland and the eyes. That's what happened with Mrs. Bush. In fact, the steps her doctors took in treating her provide a good illustration:
People diagnosed with Graves' disease are usually started on antithyroid medication---drugs that stop overproduction of thyroid hormones. These drugs are taken until the disease goes into remission, says Leonard Wartofsky, M.D., chief of the endocrine-metabolic service at Walter Reed Army Medical Center, where Mrs. Bush was treated. "We try to determine whether their hyperthyroidism may go into remission during drug treatment within a reasonable period of time---usually 6 to 18 months."
Methimazole, the antithyroid drug prescribed for Mrs. Bush, is often the only treatment that patients need. When remission doesn't occur, further therapy is necessary. "In older patients, our first concern is always their cardiac status," Dr. Wartofsky explains. "Hyperthyroidism may impose considerable stress on the heart. In such patients, we're more likely to abandon antithyroid drugs earlier and progress to radioactive iodine therapy of the thyroid."
That was the treatment course in Mrs. Bush's case. To permanently cool her overactive thyroid, Mrs. Bush drank a solution of radioactive iodine. The hormone-producing cells of the thyroid absorb the iodine and are killed by the radioactivity. The result: a defunct thyroid. Sounds drastic, but radioactive iodine has been a standard hyperthyroid treatment for more than 50 years. The iodine is trapped in the thyroid or is excreted by the kidneys, destroying thyroid cells without damaging other tissues or causing side effects. The resulting underfunctioning thyroid gland can then be easily corrected with daily doses of replacement hormone.
The iodine treatment and thyroid hormone failed to solve Mrs. Bush's eye problems, however. To treat the inflammation that was causing those problems, doctors first tried large doses of steroids. But long-term steroid use can cause serious side effects, including softened bones and diabetes. So earlier this year, Mrs. Bush began the first of 10 treatments in which low-dose radiation beams are aimed at her eyes. When done properly, this procedure is painless and produces no side effects. The radiation beams are targeted at the swollen tissue behind the eyes, avoiding the eyeballs themselves. The radiation should help relieve the pressure that's causing her eyes to bulge and reduce the inflammation of her eye muscles that's causing her double vision.
GETTING THE RIGHT MEDICINE
Whatever your thyroid problem, chances are you take thyroid hormone to treat it. In hypothyroidism, thyroid hormone restores metabolism to normal. And most people diagnosed with hyperthyroidism ultimately take thyroid hormone, too. As with Mrs. Bush, their thyroids often are purposely knocked out of action, which results in hypothyroidism; normal levels of hormone are then restored by a daily thyroid-hormone tablet.
More people take thyroid hormone for other thyroid maladies. Since these occur mainly in women, it's not surprising that thyroid hormone ranks as one of the drugs that women take most often.
Once a woman starts taking thyroid hormone, she usually takes it every day for the rest of her life. With that kind of long-term therapy, a drug should produce consistent effects. That's why a synthetic thyroid hormone is much preferred over the older, natural variety.
Today's thyroid medicine of choice is levothyroxine sodium. This newer, manmade version of natural thyroid hormone costs only about 15 cents a day.
But, unfortunately, not everyone uses the synthetic type. A study published last year in the Journal of the American Medical Association (May 12, 1989) found that many older people still take the natural kind, obtained from the thyroid glands of slaughtered animals. But in this case, "natural" may not be as healthy as synthetic. The thyroid hormone obtained from animals is unpredictable. The kind of animals used, what they ate, the season they were slaughtered---all can cause the hormone's potency to vary from one batch to another.
By contrast, the synthetic variety is pure, standardized from batch to batch and identical in chemical structure to human thyroid hormone. Many doctors have switched their patients from natural to synthetic thyroid, and some believe that all patients should switch.
"There is no longer a role for animal thyroid in the treatment of hypothyroidism," says Dr. Gambert. He's particularly concerned about the many elderly patients who've been taking animal thyroid for years---and who often are no longer under a doctor's care. Dr. Gambert urges them to contact their doctor to get their medication reassessed. If you're taking animal thyroid, ask your doctor if synthetic thyroid might be a better choice. No one should take any hormone preparation without consulting a doctor.
There's also good reason to have yourself rechecked if you've been on thyroid hormones. Until about 1960, doctors believed that a sluggish thyroid caused many common maladies. Lacking accurate thyroid-function tests, doctors prescribed thyroid hormone on a hunch rather than with solid evidence that patients needed it. So it's possible that some people who haven't checked with their doctor since getting a prescription long ago for thyroid hormone may be taking the medication for nothing.
It's now known that thyroid hormone should be used only for specific disorders, such as hypothyroidism, benign goiter, thyroid nodule and cancer of the thyroid. Taking unnecessary thyroid probably isn't dangerous for most people, but it's risky for some. If you're on thyroid medication but think you might not need it, don't discontinue therapy on your own. You can withdraw safely, but only under a doctor's care.
GETTING THE RIGHT DOSE
Doctors take special care to prescribe the minimal effective thyroid- hormone dose for people with weak hearts---some elderly and others at risk for coronary-artery disease. For these people, excess thyroid hormone may cause a heart attack or worsen coronary-artery disease. Now evidence suggests that doctors should take the same care when administering thyroid to other patients: women young and old.
Until recently, long-term treatment with thyroid hormone was considered relatively safe. Doctors didn't worry much about giving more hormone than the woman needed, as long as it didn't produce symptoms of hyperthyroidism.
In the last few years, however, studies have shown that too much replacement thyroid hormone may increase a woman's risk for osteoporosis, the bone-thinning disorder that can lead to fractures of the hip and vertebrae.
One of those studies appeared two years ago in the Journal of the American Medical Association (June 3, 1988). The study involved two groups of women: 31 premenopausal women who'd been receiving levothyroxine for more than five years and 31 other women of the same age and weight who weren't taking thyroid medication. Using a special technique, doctors measured the hip-bone densities of women in both groups.
The women being treated with thyroid hormone had significantly lower hip-bone densities than women not on thyroid. The differences were most striking in women over 35. The scientists reported that "many of the subjects" were receiving doses of thyroid hormone that would now be considered excessive.
"When using thyroxine therapeutically, one must choose the dosage with great care," says David S. Cooper, M.D., an endocrinologist at Johns Hopkins University School of Medicine. Dr. Cooper warns that "a large number of patients" face an increased risk of bone loss because their thyroid-hormone dose is too high. Luckily, there's now a way to pinpoint the optimum dose.
GETTING THE RIGHT TEST
Until recently, doctors lacked a sensitive test of "thyroid function"---a way to gauge if the gland was over- or underactive and by how much. But now a sophisticated new test can diagnose thyroid problems that have gone unrecognized in the past. And it allows doctors to gauge the optimum dose of replacement thyroid hormone that best suits each patient's needs.
The old thyroid function test measures blood levels of the main thyroid hormone, thyroxine. But a wide range of thyroxine levels can be considered "normal." A "low- normal" reading may be O.K. for one person's metabolism but too skimpy for another's. Using a highly sensitive technique, the new test measures a different hormone, thyroid stimulating hormone, or TSH.
TSH comes from the pituitary gland and does what its name suggests: stimulates the thyroid to release its hormone. The pituitary sends out TSH in response to the amount of thyroid hormone it senses in the blood. A high TSH level tells you the thyroid isn't making enough hormone.
Normal TSH levels vary less than normal levels of thyroid hormone, making TSH values easier to interpret. A low thyroxine reading, for example, suggests---but doesn't prove---that you have hypothyroidism. Using the new TSH test, your doctor may not need to do other blood tests; a high TSH level confirms that hypothyroidism is present. And in most cases, the test can detect both hypo- and hyperthyroidism.
If you think you have a thyroid disorder, the American Thyroid Association recommends that you ask your doctor for a TSH blood test.
The TSH test can also help the three million Americans already on thyroid therapy. Their need for replacement hormone may change over the years. An annual TSH test lets doctors fine-tune your dose: giving enough for normal metabolism, but not an excess that could increase osteoporosis risk.
For free information on thyroid problems, write to the Thyroid Foundation of America, Inc., Massachusetts General Hospital, ACC7305, Boston, MA 02114. To locate a qualified thyroid specialist near you, call the American Thyroid Association, Walter Reed Army Medical Center, Washington, D.C., at (202) 882-7717.