Thousands upon thousands of persons have studied disease. Almost no one has studied health.

--Adelle Davis, Let's Eat Right to Keep Fit

Of all the problems that can block Renewal, undermine health, and accelerate the aging process, none is more common--or more likely to be overlooked--than an underactive thyroid gland. And if your thyroid doesn't work right, the rest of your body doesn't, either.

Hypothyroidism, the medical term for an underactive thyroid, has such an unbelievably broad range of subtle symptoms that it is often undiagnosed or misdiagnosed. Experts estimate that undetected hypothyroidism has reached epidemic proportions in the United States, affecting between 25 and 40 percent of the nation's population.

Because a malfunctioning thyroid can thwart your bid to achieve maximum life span, you owe it to yourself to make sure that your gland is in good working order. A simple, 10-minute at-home test can tell you whether you have subclinical hypothyroidism ("subclinical" means that it displays no obvious, clearly defined symptoms). If you do, you can treat the condition safely, effectively, and inexpensively with thyroid hormone replacement.

A Grand Little Gland

The thyroid gland sits in the front of your neck, just below and to either side of your Adam's apple. In size and shape, the gland resembles a butterfly. Its rather diminutive size--it weighs less than an ounce--belies its importance.

The hormone produced by your thyroid travels through your bloodstream to receptor sites on each and every cell in your body. Once it "docks," the hormone sets the rate of cellular metabolism. In other words, it tells the cell how fast to work.

The amount of thyroid hormone that is available in your bloodstream determines each cell's metabolic rate. If the hormone is in short supply, cells behave sluggishly. Their impaired performance can translate into any of a number of health problems, depending on the types of cells involved.

If a thyroid hormone deficiency affects nerve cells, for example, thinking may slow down, or depression may set in. If it affects muscle cells, strength declines. If it affects intestinal cells, the digestion of food and absorption of nutrients may be compromised. If it affects skin cells, acne, eczema, hair loss, and other dermatologic disorders may occur.

The immune system is especially vulnerable to low levels of thyroid hormone. White blood cell production slows down, and lymphocytes lose the aggressiveness with which they usually attack and remove infectious and allergenic invaders.

Because thyroid hormone regulates metabolic activity within the endocrine system, a hormone deficiency obstructs the functioning of the system's glands and organs. (The thyroid itself is part of the endocrine system.) These components, which also include the thymus gland, adrenal glands, pancreas, ovaries, and testicles, may be unable to maintain their own hormone outputs at optimum levels. This decline in hormone production can lead to an array of physical symptoms: fatigue (adrenal glands), digestive dysfunction (pancreas), infertility and menstrual irregularities in women (ovaries), and infertility in men (testes).

Signs of a Shortfall

Hypothyroidism is a great masquerader, with vague symptoms that can mimic those of scores of other ailments. Many people who have the condition don't even realize it. In fact, the American Association of Clinical Endocrinologists estimates that only half of those afflicted have actually been diagnosed. No wonder hypothyroidism was dubbed the unsuspected illness by pioneering endocrinologist Broda Barnes, M.D., Ph.D. Dr. Barnes's pioneering work has brought greater understanding of the thyroid gland's pivotal role in human health.

The symptoms of hypothyroidism usually arise from the sluggish behavior of another organ or system within the body. Without thyroid hormone to give it marching orders, the organ or system simply doesn't know quite what to do. Nothing is whipping it into action. As a result, the organ or system just languishes, a victim of hormone deficiency.

The single most common complaint among people with underactive thyroids is low energy. But since the condition can cause any organ or system to function below par, symptoms can include heart palpitations, high cholesterol, digestive problems, constipation, circulatory problems, anemia, allergies, frequent infections, sleep disturbances, fatigue, muscle weakness, hair loss, dry skin, acne, eczema, infertility, premenstrual syndrome, memory loss, depression, difficulty losing weight, and intolerance of extreme heat or cold. All of these are physical manifestations of the metabolic slowdown that accompanies thyroid hormone deficiency. You can see why doctors so often fail to suspect hypothyroidism. They're dealing with a condition that takes many forms.

An underactive thyroid can contribute to more serious health problems as well, including heart disease, immune disorders, nervous system disorders, and the like. In such cases, treating the presenting symptoms--the obvious, outward signs of illness--won't be effective unless the underlying thyroid imbalance is corrected as well.

An Unusual Suspect

Most people go to their doctors with some idea of what's wrong with them--"My neck hurts," "This wart won't go away," "My allergies are acting up." But I've yet to have a patient say to me, "Dr. Smith, my thyroid gland is bothering me." It's always something else.

One of my patients, Ellen, said that she felt cold all the time. Herb had high blood pressure. Mary complained of constant fatigue. Joe's eczema drove him crazy. Sue couldn't lose weight. Al suffered from chronic headaches. Elizabeth struggled with severe premenstrual syndrome. Mel lost all interest in sex. Jenny couldn't get pregnant (and no, she isn't married to Mel). Jeff couldn't shake his allergies. Carol was plagued by recurrent infections. Michael didn't have any symptoms at all--just elevated cholesterol. When tested, every one of these people had an underactive thyroid.

I've found that certain symptoms serve as fairly accurate predictors of hypothyroidism. I usually test for the condition whenever a patient has one or more of the following: high cholesterol, anemia, allergies, fatigue, infertility, premenstrual syndrome, chronic infection or illness, or temperature intolerance.

The Age Factor

Age plays a part in hypothyroidism. While anyone can develop the condition, it is especially common in people over 50. In fact, it is the most often overlooked diagnosis in this age group.

As you get older, thyroid function declines. The gland's once-abundant hormone output dwindles to a mere trickle. (This phenomenon affects all of the glands and organs that produce anti-aging hormones, not just the thyroid.) The resulting hormone deficiency can speed up aging. And--here's the real kicker--it can produce physical and mental changes that mimic the aging process itself.

Just think of the sorts of ailments normally associated with growing old: fatigue, circulatory problems (feeling cold), dry skin, depression, digestive problems, memory loss, muscle weakness. Every one of these can result from a thyroid hormone deficiency.

The distinction may not seem important until you consider this: When a person over 50 experiences some type of physical or mental decline, both doctor and patient may write it off as "normal aging." They may not even discuss treatment. Yet thyroid hormone replacement could make all the difference in the world.

This brings to mind a patient of mine by the name of Sam Goodwin. A retired business executive in his seventies, Sam had been healthy all of his life. But then he started to experience a puzzling array of symptoms. He felt cold and tired most of the time. He had trouble remembering things. He no longer cared about sex. His entire body seemed to be shutting down. He mentioned all of this to his doctor, who simply replied, "You're getting up there, Sam. What do you expect?"

Needless to say, the doctor's remark didn't sit well with Sam. That's when he came to see me. All of his laboratory tests checked out fine. But his basal metabolic temperature was running about ½šF low, a good indicator of hypothyroidism. (I'll explain basal temperatures a bit later in the chapter.)

I started Sam on a trial dose of thyroid hormone. Within a few weeks, he reported noticeable improvements in his stamina, his memory, and his libido. I continued to monitor Sam's treatment for a few months, adjusting the hormone dose a couple of times. Within six months, his initial symptoms had all but disappeared.

Clearly, Sam's problems had nothing to do with "normal aging." They were the handiwork of an underactive thyroid gland. And Sam is not alone: Millions of folks suffer from hypothyroidism. Unfortunately, the majority of them have not been tested or treated for the condition.

Diagnosing Hypothyroidism

If you have any of the conditions listed in "Signs of Trouble" on page 436, you may very well have an underactive thyroid gland. In that case, check your basal metabolic temperature (BMT), using the guidelines presented in "Testing Yourself for Hypothyroidism." If your temperature is consistently below 97.8šF, you probably have an underactive thyroid. Report your findings to your doctor, along with any other symptoms you've been experiencing.

You want your doctor to perform two blood tests. One test measures your baseline level of thyroid-stimulating hormone (TSH), a substance secreted by the pituitary gland that instructs the thyroid to produce and release its own hormone. The other, called an antithyroid antibody panel, determines whether your immune system is manufacturing antibodies that may attack your thyroid. Positive results on these tests, along with low BMT and typical symtoms, confirm the diagnosis of an underactive thyroid.

Most doctors, myself included, look at the overall symptoms and correlate them with the test results. Often, the lab tests come back normal, even though the patient's BMT and symptom profile point to hypothyroidism. In such a situation, the doctor may prescribe a low dose of natural thyroid hormone on a trial basis. For a patient who has no serious illness, such a trial poses little risk, and its potential benefits are enormous.

What if your doctor dismisses your symptoms as "normal aging" and nothing more? Then you need to find another doctor who will take your concerns seriously. It may take a bit of legwork on your part--but hey, we're talking about your health and longevity here. (If you're not sure where to begin your search, you may want to consult one of the organizations listed in Resources and References on page 537.)

Determining Dosage

Once you and your doctor agree to try thyroid hormone replacement, he must figure out the proper dosage. He must also monitor your treatment and adjust your dosage as necessary. (This is another reason why having a doctor whom you feel comfortable with and trust is so critical.)

Your level of thyroid-stimulating hormone is the best indicator of the effectiveness of hormone replacement. As thyroid hormone rises, thyroid-stimulating hormone falls. Ideally, however, thyroid-stimulating hormone should drop no lower than 0.5 to 1.0 international unit per milliliter. If it does, then your thyroid hormone dosage is too high. (BMT doesn't necessarily return to normal with hormone replacement, so it isn't a very good tool for assessing whether a dosage is adequate.)

When I put a patient on thyroid hormone replacement, I check her level of thyroid-stimulating hormone every month for the first two or three months. Then once I've established the optimum dosage, I check the level of thyroid-stimulating hormone three or four times a year. Finding that optimum dosage is absolutely essential. Undertreatment can allow deficiency-related disease to get a foothold. Overtreatment can raise the patient's risk of osteoporosis.

Just as dosage is important, so, too, is the type of hormone you take. I prescribe only natural thyroid hormone replacement for my patients. You should insist on the same. The synthetic stuff does not replace the full spectrum of thyroid hormones that your body produces. Natural hormone supplements do.

Natural thyroid hormone is available only by prescription. Don't confuse it with over-the-counter thyroid glandular support formulas. These support thyroid function, but they can't correct a hormone deficiency. In fact, these products have had all of the active thyroid hormone removed.

Personal Proof

Regardless of whether you need thyroid hormone replacement, you can take other steps to ensure that your thyroid gland operates at peak efficiency. The nutrients provided by the Anti-Aging Diet and the Anti-Aging Supplement Program help keep your thyroid in tip-top condition.

Hormone replacement gives a reluctant thyroid a much-needed boost. In doing so, it makes a dramatic difference in how you feel and perform. I know, because I speak from firsthand experience.

A couple of years ago, I developed fatigue that I just couldn't seem to shake. At first, I chalked it up to a hectic schedule. But when the tiredness persisted, I decided to check my BMT. Much to my surprise, my temperature was more than 1šF below normal--a clear indication of hypothyroidism.

After a blood test to determine my baseline level of thyroid-stimulating hormone, I began taking a small dose of natural thyroid hormone every morning. Initially, the treatment didn't seem to help (which, by the way, is fairly typical). But after a month, I felt better. And after two months, my fatigue completely disappeared. The improvement was so gradual, though, that I barely noticed it.

If you are among the large percentage of the population with hypothyroidism, you, too, may be amazed at how much younger you feel once thyroid health is restored. Thyroid hormone replacement does work slowly, however. You need to give it at least three months. Just be patient. The results are well worth the wait.

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We have one final component of the Renewal Anti-Aging Program to cover. What is it? Why, exercise, of course. Renewal simply can't take place without it. The next chapter explains why.