Illustration: Nicole Kaufman
The thyroid has a big job: The hormones it secretes help regulate heart rate, maintain healthy skin, and play a crucial part in metabolism. When the gland is sluggish (hypothyroidism), it can rob you of energy, dry out your skin, make your joints ache, cause weight gain, and kick-start depression. When it becomes overworked—hyperthyroidism—and produces too much hormone, it can cause racing heart, sleep disturbances, and weight loss. That's a lot of grief for a gland the size and shape of a buckeye butterfly.

Given what can go wrong, you may be surprised to hear that about half of the estimated 27 million Americans with thyroid disease remain undiagnosed, according to the American Association of Clinical Endocrinologists. As Oprah discovered, the seemingly unrelated symptoms are partly to blame. People can spend years going from internist to specialist trying to get a diagnosis. They're often prescribed skin creams and antidepressants when what they really require is thyroid medication.

Most people with thyroid disease, about 80 percent, have the hypo version. Should symptoms drive you to make a doctor's appointment, one of the first things your physician will ask is if you have a relative with the disease, since thyroid disease tends to run in families. Your risk also increases as you get older; in addition, being female (the disorder is as much as eight times more common in women), or having another autoimmune disorder such as type 1 diabetes or rheumatoid arthritis can worsen your odds.

Depending on your risk profile, your doctor may recommend a thyroid-stimulating hormone (TSH) blood test. TSH is released by the pituitary gland; when the thyroid bogs down, the pituitary releases more TSH. If you have normal levels of TSH, your test score will be from 0.4 to 2.5. A score between 0 and 0.4 is hyperthyroidism. Between 2.5 and 4 means you are at risk for hypothyroidism, and should be retested within a year. Above 4 means you have a mild case. Doctors used to resist treating patients in this category (clinical hypothyroidism starts at 10). But a 2007 British study in The Journal of Clinical Endocrinology & Metabolism suggests that treating such patients can help prevent cardiovascular disease by reducing bad, LDL cholesterol and the risk of hardened arteries while improving waist-to-hip ratio and increasing energy. So if your symptoms led to a TSH test and you scored higher than 4, you and your doctor should discuss treatment.

While Oprah's thyroid problems seem to have stabilized and she has gone off her medications, most people with hypothyroidism face a lifetime of managing the gland. You'll get a prescription for synthetic thyroxine, which does an excellent job of replacing the missing hormone. Once you and your doctor work out the proper dosage—and that can take some time—you will feel better.

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