The job of the thyroid is to concentrate iodine from food and water to produce 100 to 125 micrograms of thyroxin (T4) each day and smaller quantities of triiodothyronine (T3), hormones that play a vital role in every aspect of metabolism–from how fast your heart beats to how efficiently you burn calories.
In one way or another, these thyroid hormones influence chemical interactions in virtually every cell of your body. They affect the speed of your heart and central nervous system, secretions of your gastrointestinal tract, your breathing rate, muscle strength, bone density, cholesterol and even your mood and personal appearance.
An infant without healthy thyroid function is at risk of severe physical and mental retardation, known as cretinism. An older child may have delayed puberty, stunted growth and brain development and symptoms similar to those of attention deficit disorder. Of the 13 million Americans with thyroid disorders, however, the majority are older adults, many of whom go undiagnosed, but usually with much less serious consequences.
Two major thyroid disorders are hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid). Both can be detected through a simple blood test measuring levels of thyroid stimulating hormone (TSH), a substance that regulates the rate at which thyroid hormones are produced. This article focuses on hyperthyroidism.
HYPERTHYROIDISM
With hyperthyroidism, TSH levels in the blood are low, thyroid hormones are high and the body is set on fast forward. In addition to an enlarged thyroid, a doctor will note a rapid pulse; moist, smooth skin; and a slight tremor at the fingertips.
If the overactive thyroid is caused by an autoimmune reaction (a disorder known as Graves’ disease), the most visible symptom is bulging of the eyeballs and a wide-eyed, surprised look. This is caused by an inflammation (swelling) behind the eyes.
Other signs include restlessness, weakness, weight loss, heat intolerance, increased sweating, diarrhea, heart palpitations and an increased heart rate. As with hypothyroidism, these symptoms develop gradually and are often mistaken for nervousness or psychiatric disorders such as mania or panic disorder. Some patients develop a lumpy, reddish thickening of the skin in front of the shins, known as pretibial myxedema.
While most Americans fantasize about having a fast metabolism and being able to eat freely with little worry of weight gain, the reality of the disorder is not so desirable. Imagine losing weight, despite a good appetite, to the point where you are so weak that it’s difficult to carry more than three books at a time. Picture what it would be like to have a hand tremor that makes it impossible for you to write clearly. Envision yourself with a fluttering sensation and chest discomfort after climbing just one flight of stairs. These are all common problems with hyperthyroidism.
Causes
The causes of excessive thyroid hormones include Graves disease, a form of toxic goiter, pituitary tumors, hormone producing thyroid tumors and temporary conditions such as illness or drug reactions. Graves disease is a common type of toxic goiter that often occurs in women. Signs of Graves disease include goiter, protruding eyeballs and general symptoms of hyperthyroidism.
Among women with normal pregnancies about 1.4 percent show some signs of overactive thyroid, including a rapid heartbeat, an increase in body temperature and tremor. The symptoms usually subside at the end of pregnancy.
Worldwide, iodine deficiency is the leading cause of thyroid disorders, but in the United States, where iodized salt has been common for many years, there is more likely a genetic or environmental cause. The latter include exposure to radiation, medications such as beta blockers and lithium, birth control pills, chronic illness and, some believe, hormone-disrupting chemicals in commercially processed foods.
Treatment
If high thyroid levels are caused by an inflammation of the gland, antithyroid medications may be prescribed. The most common treatment uses radioactive iodine to destroy thyroid cells. Another option is surgical removal of the thyroid, an option usually reserved for cases in which thyroid cancer is suspected. Other drugs such as beta blockers can be used to manage symptoms such as increased heart rate and nervousness.
All three of these treatments are usually effective in the short term, but eventually, because of the attack on the gland itself, most patients develop hypothyroidism which must be treated long term with levothyroxine.
Both hypothyroidism and hyperthyroidism are frequently triggered by an autoimmune response–an antibody in the blood that destroys or overstimulates the thyroid. And the presence of this antibody tends to run in families. Considering the vital role thyroid hormones play, thyroid disorders are relatively easy to treat. And even though many patients go undiagnosed, a simple blood test can determine the need for treatment.
2008
Michelle Herbert Thomas, PharmD, CDE
Clinical Director, Richmond Apothecaries, Inc.
