Overactive Thyroid

What Causes an Overactive Thyroid?

A number of different conditions can cause an overactive thyroid. Some of these causes include:
  • Graves' disease (the most common cause)
  • Thyroid nodules
  • Thyroiditis (inflammation of the thyroid gland)
  • Consuming too much iodine (iodine-induced overactive thyroid)
  • Taking too much synthetic thyroid hormone (a common treatment for hypothyroidism)
  • A pituitary adenoma.
Graves' disease affects about 2 percent of all women at some point in their lives. It tends to affect women between the ages of 20 and 40. Graves' disease can also affect males, infants, children, and the elderly.
(Click Causes of Overactive Thyroid for more details about these conditions.)

Signs and Symptoms

There are many symptoms or combinations of symptoms that a person with an overactive thyroid may develop. Sometimes, a person may not even have symptoms; in these cases, the condition is diagnosed based on blood tests. This is known as subclinical overactive thyroid.
A few of the possible symptoms of overactive thyroid include:
  • Fatigue
  • Increased sweating
  • An intolerance for heat
  • Weight loss, even though the person is not trying to lose weight
  • A goiter, which is an enlarged thyroid that may cause the neck to look swollen.
Age may affect the symptoms a person has. For example, older adults may lose their appetites, whereas younger people tend to have increased appetites. Older adults may also seem disinterested or withdraw socially. This is why hyperthyroidism may be misdiagnosed as depression or dementia in older adults.
(Click Symptoms of Overactive Thyroid for a longer list of possible symptoms seen with this condition.)
Last reviewed by: Arthur Schoenstadt, MD
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