The Family Health Guide

The lowdown on thyroid slowdown

Midlife can bring subtle changes in our skin, hair, energy, weight, and even mental outlook. Before writing them off as products of aging, it's a good idea to make sure they're not the result of an underactive thyroid. This tiny butterfly-shaped gland influences virtually every organ system in the body. The hormones it secretes into the bloodstream play a vital role in regulating metabolism — the rate at which our bodies convert food and oxygen to energy. Low thyroid hormone production, or hypothyroidism, causes a range of symptoms— fatigue, constipation, dry skin and brittle nails, aches and pains, and feeling down — that you might easily attribute to other health problems.

Hypothyroidism is especially common in women. Between ages 35 and 65, about 13% of women will have it, and the proportion rises to 20% among those over 65. Because the link between symptoms and thyroid disease isn't always obvious many women won't know they have it — and won't be treated for it.

Untreated hypothyroidism can increase your risk for high cholesterol, high blood pressure, and heart disease. Hypothyroidism can be diagnosed with a blood test and treated with a pill.


The symptoms of hypothyroidism can differ from person to person and can come on gradually or abruptly.

Characteristic signs of hypothyroidism include:

  • Fatigue. Low thyroid function can result in less energy.
  • Cold intolerance. Slowed-down cells burn less energy, so the body produces less heat.
  • Appetite loss, weight gain. With lower energy needs, you require fewer calories, so your appetite declines. Yet, your body converts fewer calories into energy, so you may gain a few pounds.
  • Cardiovascular effects. Low levels of thyroid hormone can lead to high blood pressure, elevated levels of cholesterol, and increased homocysteine (a risk factor for heart disease). The heart's pumping ability may slow increasing the risk of congestive heart failure, especially in older women.
  • Mental effects. Hypothyroidism and depression share many of the same symptoms, including difficulty in concentrating, memory problems, and loss of interest in things that are normally important to you. They call for different treatments, so proper diagnosis is important.
  • Other signs and symptoms. Slowed metabolism reduces sweating, so the skin may become dry and flaky and nails brittle. Hair may thin or become coarse. Digestive processes slow, causing constipation. Speech and movement may also slow down. In younger women, periods may become heavier and more frequent, or they may stop; infertility is sometimes a problem. Muscle aches and pain around the joints are common. Older women may have balance problems.

Diagnosing hypothyroidism

If you have any symptoms, see your clinician for a physical exam. You'll be checked for signs of hypothyroidism, such as an enlarged thyroid gland, dry skin, hair loss, weight gain, and elevated cholesterol levels. Your clinician may test your blood for levels of thyroid-stimulating hormone (TSH) — the single best screening test for thyroid disease — as well as the thyroid hormone thyroxine (T4).

Treating low thyroid

Hypothyroidism is usually treated with a daily dose of synthetic T4 (levothyroxine sodium), in pill form. Levothyroxine works exactly like your own body's thyroid hormone. The goal of drug treatment is to lower your TSH to about the midpoint of normal range and maintain it at that level. Typically, you'll start with a relatively low dose and have your TSH checked six to eight weeks later. If necessary, your physician will adjust the dose, repeating this process until your TSH is in the normal range. Once the right dose is established, your TSH and possibly T4 levels will be checked every six months to a year. Most people who take enough synthetic T4 to normalize TSH levels will find that their symptoms go away.

January 2006 Update