Understanding the thyroid
The thyroid is a small gland, shaped like a butterfly, that rests in the
middle of the lower neck. Its primary function is to control the body’s metabolism
(rate at which cells perform duties essential to living). To control
metabolism, the thyroid produces hormones, T4 and T3, which tell the body’s
cells how much energy to use.
A properly functioning thyroid will maintain the right amount of hormones
needed to keep the body’s metabolism functioning at a satisfactory rate. As
the hormones are used, the thyroid creates replacements. The quantity of thyroid
hormones in the bloodstream is monitored and controlled by the pituitary gland.
When the pituitary gland, which is located in the center of the skull below the
brain, senses either a lack of thyroid hormones or a high level of thyroid
hormones, it will adjust its
own hormone (TSH) and send it to the thyroid to tell it what to do.
What is thyroid disease and whom does it affect?
When the thyroid produces too much hormone, the body uses energy faster than
it should. This condition is called hyperthyroidism. When the thyroid doesn’t
produce enough hormone, the body uses energy slower than it should. This
condition is called hypothyroidism. There are many different reasons why either
of these conditions might develop. Currently, about 20 million Americans have some
form of thyroid disease. People of all ages and races can get thyroid disease.
However, women are five to eight times more likely than men to have thyroid problems.
What causes thyroid disease?
There are several different causes of thyroid disease. The following
conditions cause hypothyroidism:
- Thyroiditis is an inflammation of the thyroid gland.
This can lower the amount of hormones produced.
- Hashimoto’s thyroiditis is a painless disease of the
immune system that is hereditary.
- Postpartum thyroiditis occurs in 5 percent to 9 percent of women after
giving birth. It is usually a temporary condition.
- Iodine deficiency is a problem affecting approximately
100 million people around the world. Iodine is used by the thyroid to
produce hormones. Although prevalent before the 1950s in the USA, iodine
deficiency has been virtually wiped out by the use of iodized salt.
- A non-functioning thyroid gland affects one in 4,000 newborns. If the problem isn’t corrected, the child will be
physically and mentally retarded.
The following conditions cause hyperthyroidism:
- With Graves’ disease, the entire thyroid gland might be
overactive and produce too much hormone. This problem is also called diffuse
toxic goiter (enlarged thyroid gland).
- Nodules might be overactive within the thyroid. A single
nodule is called toxic autonomously functioning thyroid nodule, while several
nodules are called a toxic multi-nodular goiter.
- Thyroiditis, a disorder that can be painful or painless,
can also release hormones that were stored in the thyroid gland causing
hyperthyroidism for a few weeks or months. The painless variety occurs most
frequently in women after childbirth.
- Excessive iodine is found in a number of drugs such as
Amiodarone, Lugol’s solution (iodine), and some cough syrups, and might cause
the thyroid to produce either too much or too little hormone in some
What are the symptoms of hypothyroidism and hyperthyroidism?
The following are symptoms for hypothyroidism:
- Frequent, heavy menstrual periods
- Weight gain
- Dry, coarse skin and hair
- Hoarse voice
- Intolerance to cold
The following are symptoms for hyperthyroidism:
- Muscle weakness/tremors
- Infrequent, scant menstrual periods
- Weight loss
- Sleep disturbances
- Enlarged thyroid gland
- Vision problems or eye irritation
- Heat sensitivity
How is thyroid disease diagnosed?
Thyroid disease can be difficult to diagnose because symptoms are easily
confused with other conditions. Fortunately, there is a test, called the thyroid
stimulating hormone (TSH) test, that can identify thyroid disorders even before
the onset of symptoms. The Journal of the American Medical Association
found that screening for mild thyroid failure in women and men over age 35 is as
cost-effective as screening for more common problems such as high cholesterol or
high blood pressure.
When thyroid disease is caught early, treatment can control the disorder even
before the onset of symptoms.
How is thyroid disease treated?
The goal of treatment for any thyroid disorder is to restore normal blood
levels of thyroid hormone.
Hypothyroidism is treated with a drug called levothyroxine. This is a
synthetic hormone tablet that replaces missing thyroid hormone in the body. With
careful monitoring, your doctor will adjust your dosage accordingly, and you’ll
soon be able to return to your normal lifestyle.
Hyperthyroidism, generally more difficult to treat, requires the
normalization of thyroid hormone production. Treatment could involve drug
therapy to block hormone production, radioactive iodine treatment that disables
the thyroid, or even thyroid surgery to remove part or the entire gland.
The most popular treatment is radioactive iodine. This therapy often results
in hypothyroidism, requiring the use of levothyroxine (synthetic replacement
hormone) in order to restore normality.
Thyroid diseases are life-long conditions. With careful management, people
with thyroid disease can live healthy, normal lives.
Copyright 1995-2006 The Cleveland Clinic Foundation. All rights reserved