Often, the thyroid is the real culprit

It is one of the stealthiest of human maladies: hypothyroidism. Resulting from an underactive thyroid gland, it can produce depression, weight gain, high cholesterol, fatigue and a wide range of other symptoms, each of which may look like a disorder all by itself. Even though it’s the true culprit, the malfunctioning of the thyroid may never be detected, while the symptoms are being aggressively treated -- often ineffectively.

But that may be changing. These days the thyroid, like a schoolchild waving for attention, is finally getting a lot more notice. Recent research suggests that as many as one in 10 Americans may suffer from an underactive thyroid. That revelation has given added credibility to those who argue that the gland should be tested routinely, just as the heart is regularly examined.

The thyroid sits in the front of the throat, like a bow tie below the Adam’s apple, quietly secreting hormones that circulate through the bloodstream to every cell of the body. When the gland goes awry, producing too little hormone (hypothyroidism) or too much hormone (hyperthyroidism, a much less common condition), body and mind are thrown out of sync. Too little of the thyroid hormone causes a body-wide slowdown.

Testing and treatment

One current debate is whether people with slightly underactive glands should be treated.

The blood test for hypothyroidism is inexpensive and easy. So is the treatment. A daily dose of thyroid hormones replaces what a sluggish gland fails to make on its own.

As for diagnosis, there are several indications of hypothyroidism. One is an elevated level of a thyroid-stimulating hormone in the blood. Usually called TSH, it is the chemical signal that the pituitary gland sends to prompt the thyroid into action. Another test is a direct measurement of the amount of thyroid hormone in the blood.

But the amount of that hormone may be normal because the increasing amount of TSH is managing to keep the failing thyroid pumping adequately. That’s why an elevated level of the stimulating hormone is so telling.

Some of the most obvious, but lesser, symptoms of hypothyroidism are thinning hair, dry skin and puffy eyes. These also come with age, of course, which is why they are deceptive symptoms. Other subtle signs are memory lapses, feeling chilled and trouble losing weight. Some of the indicators are so commonplace that one doctor, a hormone specialist in fact, sheepishly admits that he missed for far too long the signs that his own father, also a physician, was suffering from hypothyroidism and not just the frailty of his years.

The first of the major studies prompting the new vigilance was the Colorado Thyroid Disease Prevalence Study, published two years ago. More than 9% of the 25,000 Colorado residents tested had abnormally high TSH levels.

“That was a shocker,” says Dr. Leonard Wartofsky, chairman of the department of medicine at the Washington Hospital Center in Washington, D.C.

That study was followed by a more diverse survey of 16,000 apparently healthy Americans published this year. It found that 4.6% had hypothyroidism, even though they seemed symptom-free. The abnormal test readings were most prevalent in women, the elderly, whites and Mexican Americans.

“There’s a lot of this out there,” says Wartofsky, “and studies are showing that there’s a benefit to finding it and treating it.”

There’s no disagreement about treating anyone with clearly high levels of the stimulating hormone whether or not the patient has troubling symptoms. The most active controversy centers on people whose thyroid is just slightly underactive, a condition that has been called subclinical or mild hypothyroidism. In these people, there may be some symptoms or none at all. Nearly half of those with mild hypothyroidism, according to Wartofsky, will develop the full-blown disease in five to seven years.

On the testing issue, some kind of consensus among experts is expected to emerge soon. But for the time being, medical organizations have been offering a bewildering array of screening recommendations.

One says that men and women over 35 years old should have a blood test every five years. Another recommends annual screening for those over 60, especially women. A third puts the spotlight on just about anyone with a family history of thyroid problems.

Meantime, the federal group responsible for guidelines, the U.S. Preventive Services Task Force -- looking at costs as well as potential benefits -- is on the fence. It says, “There is insufficient evidence for or against screening.”

“It’s a hot debate,” says Inder Chopra, a UCLA endocrinologist and member of a panel currently considering a recommendation for those who qualify for Medicare.

“You would be doing so many tests,” he says, and it “wouldn’t justify the expense.”

Disease linked to aging

But E. Chester Ridgway, president elect of the Endocrine Society, maintains that studies demonstrate that thyroid testing is more cost-effective than measuring blood cholesterol and equally as cost-effective as blood pressure or mammography.

He’s critical of the federal preventive task force for “really burying its head in the sand on this one. The prevalence is going to be much higher. Everybody’s anticipating a huge shift to an older population and more chronic diseases, thyroid being one of them.”

The thyroid fails to produce enough hormone for a number of reasons. Drugs like lithium and interferon can interfere with thyroid function. An infection or shift in hormones after pregnancy or during menopause can cause a slowdown that may be temporary or permanent. Some people are born with an underactive thyroid. But the most frequent cause is an immune-system failure, often associated with aging.

One disorder frequently found in elderly women is called Hashimoto’s thyroiditis, an autoimmune condition in which the body attacks its own thyroid cells.

Ridgway says that while this disease becomes more prevalent with age, it can occur in younger people and is “far and away the most common cause of hypothyroidism in our country.”

Hashimoto’s thyroiditis, which results in the death of thyroid cells, was first described in Japan 90 years ago and has been increasing in this country for about 50 years.

According to the American Thyroid Assn., the cause is probably a combination of an inherited tendency and some trigger that has yet to be identified. There is some speculation that stress may play a role.

This thyroid disease has also been linked to a high intake of iodine. So anyone with a high TSH reading may want to check for hidden sources of iodine. Dr. John T. Dunn, a nationally recognized authority on iodine at the University of Virginia Health Sciences Center, says there is a lot of iodine in fast food, for instance.

He also points to some red food coloring, like the type that is used to color pills. People who eat kelp should know that certain types contain very high quantities. Some disinfectants, Dunn says, can be sources because iodine can be absorbed through the skin. The iodine in iodized table salt is a relatively minor concern, he says.

The paradox is that the thyroid needs some iodine to make thyroid hormone, so too little iodine can also cause hypothyroidism.

Thyroid specialists say that if you have any of the symptoms that might point to hypothyroidism and they have just recently appeared, let your physician know about it.

Your doctor may feel that a blood test is warranted. If the symptoms have been around awhile, the specialists say, it’s less likely that the thyroid is the cause.