Q: I just found out that I have subclinical hypothyroidism. What
exactly does that mean, and do I need to take medication for this
A: No, you don’t necessarily need to take medication for this
condition. But it might make sense if you feel sluggish or
– two common symptoms of low thyroid function, or
hypothyroidism. The thyroid gland, a tiny, butterfly-shaped gland
at the base of the throat, releases hormones that control how fast
the body burns energy.
By The Faculty of Harvard Medical School Advisor
Q: I just found out that I have subclinical hypothyroidism. What exactly does that mean, and do I need to take medication for this problem?
A: No, you don’t necessarily need to take medication for this condition. But it might make sense if you feel sluggish or tired – two common symptoms of low thyroid function, or hypothyroidism. The thyroid gland, a tiny, butterfly-shaped gland at the base of the throat, releases hormones that control how fast the body burns energy. If it doesn’t produce enough of these hormones, many different symptoms can result. In addition to fatigue, other symptoms include constipation, dry skin, brittle nails, weight gain, aches and pains, and feeling down.
To diagnose thyroid problems, clinicians test blood levels of two substances: thyroid-stimulating hormone (TSH) and thyroid hormone (T4). A TSH level between 0.45 and 4.5 mU/L is considered normal. A TSH level higher than 4.5 suggests hypothyroidism (see graphic). If your TSH is high and your T4 is low, that means you have the most common type of hypothyroidism: primary hypothyroidism.
But if your TSH is high and your T4 level is normal, you have subclinical or borderline hypothyroidism. There’s no agreed-upon approach to managing this condition. Most physicians decide what to do based on a person’s symptoms and family history. This may involve a trial of thyroid medication to see if you feel better. Even if you have no symptoms, your doctor still needs to repeat your blood tests every so often, since subclinical hypothyroidism can progress to full-fledged hypothyroidism.
The most common cause of primary hypothyroidism is a condition called Hashimoto’s thyroiditis. In this condition, which tends to run in families, the immune system makes antibodies that attack the thyroid gland, leaving it unable to make enough thyroid hormone. Other permanent causes of hypothyroidism include surgery (to treat cancer or other growths on the thyroid gland) and radiation (to treat thyroid or other types of cancer).
Your thyroid function also may falter due to a temporary condition, such as pregnancy or a viral infection, which causes the thyroid gland to become swollen or inflamed. Sometimes, these temporary problems can become permanent.
Certain drugs can also suppress thyroid hormone production. These include the heart-arrhythmia drug amiodarone (Cordarone); the psychiatric medication lithium; interferon alpha, which is used to treat hepatitis C and certain types of leukemia and other cancers; and the cancer drug interleukin-2.
For both subclinical and primary hypothyroidism, the treatment is simple: a daily dose of synthetic T4 (levothyroxine sodium) in pill form. Levothyroxine works exactly like your own body’s thyroid hormone. It’s available in the generic form and under such brand names as Euthyrox, Levothroid, Levoxyl and Synthroid. All brands contain the same synthetic T4, but their inactive ingredients can vary. These ingredients can affect how you absorb the drug, so it’s best to stick with one brand.
The goal of drug treatment is to lower your TSH to about the midpoint of normal range and keep it there. 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. Physicians must be careful not to give you too much because excessive doses can stress the heart and increase your risk of weak, fragile bones (osteoporosis). Once the right dose is established, your TSH and possibly T4 levels will be checked every six months to a year.
Thyroid hormone is best absorbed on an empty stomach. Don’t take antacids or supplemental iron at the same time because they can interfere with thyroid hormone absorption. Most people who take enough synthetic T4 to normalize TSH levels will find that their symptoms go away.
Hypothyroidism is especially common in women. Between ages 35 and 65, about 13 percent have it, and the proportion rises to 20 percent among those over 65. And untreated primary hypothyroidism can increase your risk for high cholesterol, high blood pressure and heart disease. If your doctor decides not to treat your subclinical condition, you should still keep an eye out for symptoms and get your thyroid levels rechecked every year.
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