Thyroid disorder messes with metabolism

Like popular media mogul Oprah Winfrey, Susan Johnson struggled with weight gain and a nagging fatigue she couldn't explain. Neither could her doctor, who attributed her symptoms -- which included dry skin, brittle nails and the loss of eyebrow hair -- to the aging process.

"I was exercising and eating healthy," said Johnson, 51, of East Grand Rapids, Mich. For years, nothing she did helped ease her symptoms. "I always felt cold, with tingling hands and feet. When I finally insisted on having a blood test, it showed that my thyroid hormone levels were low. That was the problem."

Johnson has hypothyroidism, which means that the thyroid is not producing enough hormone to regulate the body's metabolism -- how the body uses energy and controls body temperature.

A synthetic hormone replacement was prescribed. Her thyroid gland never will regain function, and Johnson will be on medication the rest of her life. But "I feel normal again," said Johnson, a marketing, communications and public relations consultant.

Dr. Donna Harold, an internist with Michigan Medical P.C. and Spectrum Health, said the symptoms of an underactive thyroid are often vague, "so most people think that they're brought on by stress or by being too busy."

Although Winfrey announced several months ago that stress played a part in her thyroid dysfunction, which caused her to gain weight and feel exhausted, she has been vague about her diagnosis and whether she is on medication. She has said reducing stress, taking vitamins and eating only fresh foods have helped ease her symptoms.

"Once the thyroid gland stops working well, it doesn't regenerate," Harold said, no matter how you change personal habits such as diet and exercise.

What Winfrey has done, however, is help more people become aware of thyroid disease, she said.

Part of endocrine system

Located inside the neck, just below the larynx, or voice box, the thyroid gland is an integral part of the endocrine system. Stimulated by the pituitary gland in the brain, it produces hormones that regulate metabolism.

When the thyroid doesn't produce enough hormones, the result is hypothyroidism. A simple blood test that measures the thyroid-stimulating hormone (TSH) can uncover the condition, Harold said.

"If you have symptoms that last a few weeks or a month, it's time to make an appointment with your doctor for an evaluation," she said.

Although hypothyroidism mainly affects women in perimenopause and menopause, it also can affect women of child-bearing age who've just gone through a pregnancy, she said. "I see women of all ages who have this thyroid condition."

Hypothyroidism can be caused by an autoimmune disease called Hashimoto's thyroiditis or removal of all or part of the thyroid or exposure to specific types of radiation, Harold said. Thyroid function also affects other organs, such as the brain, heart, liver, kidneys and skin.

Left untreated, the disorder could lead to higher triglycerides and cholesterol, poor mental and physical performance and possible heart disease. In children, the untreated condition can inhibit normal growth and mental development.

Usually, the progress of the condition is slow, and many don't know they have a low-functioning thyroid because they may have no or very few symptoms, she said.

Metabolism slows with age

For Tracy Green, 44, of Plymouth, Mich., who founded the Michigan Thyroid Disorder Support Group in 1999, signs of a thyroid problem began in adolescence.

"I started having symptoms when I was 12," Green said. "I suffered with migraine headaches, but had no other signs of a thyroid problem that would raise a red flag."

As Green got older, she experienced more typical symptoms of low-functioning thyroid, including a sensation of cold, brittle nails and exhaustion. After the birth of her second child in the mid-1990s, Hashimoto's thyroiditis was diagnosed. Hashimoto's patients often go from overactive thyroid (hyperthyroidism) to underactive thyroid (hypothyroidism), before the thyroid gland stops working entirely, she said.

"I knew there had to be other people out there who were dealing with the same thyroid issues that I was," Green said.

Hashimoto's thyroiditis is the most common cause of hypothyroidism, said Dr. Emilie Collins, an endocrinologist with St. Mary's Health Care. "It's an autoimmune condition that leads to inflammation and potential destruction of the thyroid gland," Collins said, adding that hypothyroidism is about five times more common in women than men.

Once diagnosed, hypothyroidism is treated with a thyroid replacement hormone medication, usually taken once a day for the rest of the patient's life.

Harold cautions, however, that medication may not be a cure-all.

"Even if you're on medication, your overall metabolism will slow down as you age, and there are some metabolic factors we can't change," she said. "And if the disorder has caused weight gain, the medication is not going to melt away the added pounds. You still need to do that the old-fashioned way through exercise, keeping a food diary and eating less."

Patients on thyroid hormone replacement therapy need to be monitored to make sure they're not being overmedicated, Collins said. Too much thyroid hormone can cause symptoms of hyperthyroidism, or an overactive thyroid, which include rapid heartbeat, diarrhea, weight loss, nervousness and fatigue.

After medication is prescribed, Collins recommends following up with a TSH blood test in six to eight weeks to recheck hormone levels, then follow-up testing every six months to one year while on medication.

"Hypothryroidism is an easy disease to control, if you have a physician who knows how to treat it," Green said.