DEAR DOCTOR K:
My doctor thinks I may have an overactive thyroid. What does that mean? Which of my symptoms did it cause?
Hyperthyroidism, or overactive thyroid, is a condition in which your body makes too much thyroid hormone. Thyroid hormones are made by the thyroid gland, which sits just under the skin of the lower front part of your neck.
Thyroid hormones regulate the body’s energy. When levels of thyroid hormones are unusually high, the body burns energy faster. As a result, many body processes speed up. (I’ve put an illustration comparing normal and hyperthyroid function below.)
The symptoms of hyperthyroidism tend to come on slowly, and they vary from person to person. The typical person with hyperthyroidism endures sleepless nights, heat intolerance, excess sweating, weight loss, a voracious appetite and loose bowels.
Other signs and symptoms of hyperthyroidism include:
- Enlarged thyroid gland
- Special trouble dealing with hot weather
- Emotional volatility (often with anxiety and depression)
- Nervousness and agitation
- Excessive thirst
- Racing and irregular heartbeat
- Fast pulse
- Hand tremors
- Muscle weakness
- Bulging eyes
- Lighter menstrual periods
- Generalized itching (with or without hives)
Certain symptoms are more common in people older than 65. Indeed, older people often don’t have the agitation and tremors seen in younger people with hyperthyroidism — it’s called “apathetic hyperthyroidism.” Depression and heart failure are more common in older patients. A clue that an older person has hyperthyroidism is a racing pulse: a heart rate of 90 beats per minute, even when the person is resting.
It’s not always obvious that symptoms such as excess thirst or increased appetite signal that something is wrong. People often don’t see a doctor until they experience palpitations or shortness of breath. Sometimes their family brings them to see the doctor because of personality changes.
Treatment stops the thyroid from overworking. Three different treatment options are available. One option is to use radioactive iodine to destroy part of the thyroid. Another option is to take medication that blocks the thyroid’s ability to produce hormone. Finally, surgery may be done to remove all or part of the thyroid.
If you are treated with radioactive iodine or surgery, you will most likely need to take thyroid hormone replacement pills for the rest of your life. This will replace the hormone that your body is no longer making.
Hyperthyroidism can have serious consequences if left untreated. It increases the risk for the bone-thinning disease osteoporosis. It can lead to heart difficulties, as too much thyroid hormone makes your heart work faster and harder. So it’s a good thing your doctor diagnosed the condition. I expect the treatment will be effective.
Normally, the thyroid gland lowers its output of thyroid hormones T4 and T3 when signaled to do so by a drop in TSH from the pituitary gland (left). But an overactive thyroid does not respond to this signal and continues to produce too much thyroid hormone (right). The thyroid enlarges, and a wide variety of symptoms may appear.