What is hyperthyroidism?



The thyroid is a four-to-five inch gland that sits in the neck below Adam’s apple. Its main function is to make thyroid hormones (T3 and T4), which help regulate overall metabolism. Thyroid hormones are the “thermostat” of the body helping to regulate temperature, heart rate, bowel function, energy, weight and overall feeling of well-being. Hyperthyroidism is a condition in which the thyroid produces excess thyroid hormones.   There are several causes of hyperthyroidism, but Graves’ Disease (an autoimmune condition) is the most common.


What are the symptoms of hyperthyroidism?

Not every patient has symptoms. Mild hyperthroidism may be discovered on routine blood tests.  Some common symptoms include:

  • Fatigue, muscle weakness/aches
  • Weight changes (usually weight loss but some patients experience increased appetite and weight gain)
  • Heat intolerance
  • Anxiety, irritability
  • Tremors
  • Rapid heart rate
  • Difficulty sleeping
  • Diarrhea/more frequent bowel movements
  • Irregular menstrual periods
  • Eye buldging/irritation or blurry vision (Grave’s eye disease)
What are the causes of hyperthyroidism?

Hyperthyroidism can be caused by overactive nodules (toxic nodules) or autoimmune activation of the thyroid gland (Graves’ Disease).  Occationally, patients may have temporary hyperthyroidism after an illness or as a reaction to certain medications.

Hyperthyroidism can also result from taking excessive thyroid medication.

What is Graves' Disease?

Graves’ Disease is the most common cause of hyperthyroidism, named after Irish doctor Robert Graves. It is an autoimmune disorder where the body makes antibodies that attack the thyroid gland and stimulate thyroid tissue to produce excessive amounts of thyroid hormone, which can cause hyperthyroid symptoms.  The thyroid gland may enlarge, which is commonly referred to as a ‘goiter.’

Some patients develop an additional immune reaction around the eyes, (called Graves’ eye disease or ophthalmopathy). The eyes may become very dry, irritated, and inflamed, and this may affect eye muscles and tissue behind the eyes, causing double vision, bulging eyes, and pressure or pain.  Cigarette/tobacco smoking is associated with more severe symptoms in patients with Grave’s disease.  If you are a smoker with Graves’ disease or Graves’ eye disease, it is very important to stop smoking as it can worsen your symptoms. If you need help to quit smoking, please talk to your provider.

How is hyperthyroidism treated?

There are 3 potential treatment options for hyperthyroidism.  Your doctor can help you determine what is the best treatment for you.

Antithyroid medications – Methimazole (MMI) or Propothialuracil (PTU) are prescription medications that can be used to block/lower thyroid hormones.  These medications may also be used as a temporary treatment prior to surgery or radioactive iodine treatment.

Radioactive Iodine Treatment – Usually a single dose of radioactive iodine can destroy overactive thyroid tissue.  This usually results in hypothyroidism (underactive thyroid) and need for long-term thyroid hormone replacement pills.

Surgery – Removal of the overactive thyroid (part or all) is preferred for patients with larger glands, multiple nodules, concern for cancer, patients with severe Graves’ eye symptoms, and patients that do not want to take radioactive iodine.

How is hyperthyroidism diagnosed?

Hyperthyroidism is diagnosed by routine thyroid blood tests (e.g., TSH, T4, T3 levels).   

Additional tests may be ordered to check for thyroid antibodies for patients with suspected Graves’ disease, but are not always necessary. 

Nuclear iodine uptake scans can also be helpful in determining the cause and best treatment of hyperthyroidism.  


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