Overactive Thyroid
An overactive thyroid (hyperthyroidism) occurs when your thyroid gland produces too much of the thyroid hormones.
Thisresults ina high level of thyroid hormones called triiodothyronine (also called "T3") and thyroxine (also called "T4") in your body.
The thyroid can become overactive for a number of reasons. Some of the main causes are described below.
In about three in every four cases, an overactive thyroid is caused by a condition called Graves' disease.
This is an autoimmune condition, which means the immune system mistakenly attacks the body. In Graves' disease,itattacks the thyroid and causes it to become overactive.
The cause of Graves' disease is unknown, but it mostly affects young or middle-aged women and it often runs in families. Smoking can also increase your risk of getting it.
Less commonly, an overactive thyroid can occurif lumps called nodules develop on the thyroid.
These nodules are usuallynon-cancerous (benign), but they contain additional thyroid tissue, whichcanresult in the production of excess thyroid hormones.
It's not known whysome peopledevelop thyroidnodules, but they most often affect people over 60 years of age.
An increased level of iodine in the body can cause the thyroid to produce excess thyroid hormones.
This can occasionally occur if you're taking medication that contains iodine, such as amiodarone a medicine sometimes used to control an irregular heartbeat (arrhythmia) .
An overactive thyroid caused by medication will usually improve once the medication is stopped, although it may take several months for your thyroid hormone levels to return to normal.
Other possible causes of an overactive thyroid include:
Find out about an overactive thyroid (hyperthyroidism), including what the symptoms are, why it happens and how it's treated.
Find out about the main symptoms of an overactive thyroid (hyperthyroidism) and when to get medical advice.
Find out about the main causes of an overactive thyroid (hyperthyroidism), such as a condition called Graves' disease.
Find out about the main tests used to diagnose an overactive thyroid (hyperthyroidism), including a thyroid function blood test.
Find out about the main treatments for an overactive thyroid (hyperthyroidism), including medication and surgery.
Find out about the complications that can occur as a result of an overactive thyroid (hyperthyroidism), including eye problems and pregnancy problems.