Hypothyroidism: A Consumer’s Guide to Diagnosing and Treatment

Millions of Americans are affected by hypothyroidism, a condition in which the body does not produce enough thyroid hormones. Because of an increase in the inappropriate diagnosis and treatment of hypothyroidism, The Royal College of Physicians and several other medical professional organizations in the United Kingdom issued a statement in late 2008 describing the correct management of this condition. In this article, we present their recommendations.

What are the causes and effects of hypothyroidism?

Ninety-five percent of hypothyroidism is caused by decreased production of thyroid hormone in the thyroid gland, which is called primary hypothyroidism. In some cases, decreased thyroid hormone production is related to diseases of the pituitary gland or hypothalamus in which the signals to the thyroid gland to produce thyroid hormone are deficient (called secondary and tertiary hypothyroidism, respectively).

Secondary and tertiary hypothyroidism should generally be managed by thyroid or endocrine specialists. The remainder of this article will discuss primary hypothyroidism only.

Thyroid hormones regulate cell metabolism and affect nearly every organ in the body. The symptoms of hypothyroidism include fatigue, slow movement, slow speech, cold intolerance, constipation, weight gain, menstrual irregularities and muscle pains.

In addition, hypothyroidism can also cause elevated levels of fats in the blood (hyperlipidemia), an abnormally low concentration of sodium in the blood and anemia (low red blood cell count).

When should you have your thyroid level checked?

If you have any of the symptoms described above and you or your physician suspect that you may have hypothyroidism, laboratory tests should be performed to confirm the diagnosis. This is essential because these symptoms are not specific to hypothyroidism, which can only be differentiated from other diseases that cause similar symptoms by measuring levels of thyroid hormones in the blood. This involves measuring thyroxine (T4), which is produced by the thyroid gland, and thyroid stimulating hormone (TSH), a hormone released by the pituitary gland that stimulates the thyroid to produce thyroxine.

Who should be treated?

If your laboratory tests confirm a diagnosis of primary hypothyroidism, you should be treated. Many experts believe that if you have subclinical hypothyroidism and your TSH is above 10 or 20 milliunits per liter, then you should be treated as well. Treatment of subclinical hypothyroidism may cause your symptoms to improve, and may prevent progression to overt hypothyroidism.

Some clinicians may recommend treatment with thyroid hormone replacement without confirmation that a patient has hypothyroidism with laboratory tests or with test results that are normal. We disagree because doing so may lead you to miss other causes for your symptoms, some of which can be quite serious. Also, the inappropriate use of thyroid hormone replacement in conditions such as depression or hyperlipidemia, or too high a dose when hypothyroidism is present, may result in a cardiac arrhythmia (irregular heartbeat) or osteoporosis.

What treatment is preferable?

Overwhelming evidence supports the use of synthetic T4 only in the treatment of primary hypothyroidism. Synthetic T4 is available in a number of generic and brand-name preparations (levothyroxine, brand names LEVO-T, LEVOXYL, NOVOTHYROX, SYNTHROID, THYRO-TABS, UNITROID).

Other preparations of thyroid hormone that include the thyroid hormone triiodothyronine (T3), such as liothyronine (CYTOMEL), or mixtures of T3 and T4 as found in THYROLAR or in thyroid tablets (ARMOUR THYROID), have been shown to be no better than therapy with T4 in several studies. In addition, treatment with T3 may result in wide fluctuations in levels of thyroid hormone in the blood and can complicate the measurement of thyroid hormones in the blood.

Levels of TSH should be checked periodically, typically every three to six weeks, and the dose of synthetic T4 should be adjusted until the TSH level falls within the normal range. To reduce the risk of a cardiac arrhythmia or heart attack in elderly patients or those with a prior history of coronary artery disease, synthetic T4 should be started at a low dose (25 to 50 micrograms/day) in these patients. If your symptoms continue after adequate treatment with thyroid hormone, your physician should investigate other causes for your symptoms.

Summary Points

• Symptoms of hypothyroidism can be vague and include fatigue, slow movement and slow speech, cold intolerance, constipation, weight gain, menstrual irregularities and muscle pains.
• An accurate diagnosis of hypothyroidism can be made only after confirmation with laboratory tests.
• Thyroid stimulating hormone (TSH) should be tested before thyroxine (T4), as TSH is a more sensitive test for primary hypothyroidism.
• In almost all cases, only synthetic thyroxine (T4) should be used to treat primary hypothyroidism.
• The adequacy of thyroid hormone replacement should be assessed by measuring TSH periodically until it falls to normal levels.
• If symptoms persist after correction of thyroid deficiency, other causes for your symptoms should be investigated.
• Inappropriate or excessive replacement of thyroid hormone carries risks, including cardiac arrhythmia and osteoporosis.