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What is hyperthyroidism?

Hyperthyroidism is a condition in which the thyroid gland is overactive and produces too much thyroid hormone. If left untreated, hyperthyroidism can lead to other health problems. Some of the most serious involve the heart (rapid or irregular heartbeat, congestive heart failure) and the bones (osteoporosis).

What causes hyperthyroidism?

Graves disease is the most common cause of hyperthyroidism. It occurs when the immune system attacks the thyroid gland, causing it to enlarge and make too much thyroid hormone. It typically runs in families with a history of thyroid disease or other autoimmune conditions. Some people with Graves' disease also develop swelling behind the eyes that causes the eyes to bulge outward.

Less common causes of hyperthyroidism include:
  • Thyroid nodules: Lumps on the thyroid gland that may secrete too much thyroid hormone
  • Subacute thyroiditis: A painful inflammation of the thyroid typically caused by a virus
  • Lymphocytic thyroiditis: A painless inflammation caused by lymphocytes (a type of white blood cell) inside the thyroid
  • Postpartum thyroiditis: Thyroiditis that develops shortly after pregnancy
  • Certain medications, like amiodarone and some cancer immunotherapies

What are the signs and symptoms of hyperthyroidism?

  • Feeling too hot
  • Increased sweating
  • Muscle weakness
  • Trembling hands
  • Rapid heartbeat
  • Tiredness/fatigue
  • Weight loss
  • Diarrhea or frequent bowel movements
  • Irritability and anxiety
  • Eye problems, such as irritation or discomfort
  • Menstrual irregularities
  • Infertility

How is hyperthyroidism diagnosed?

Your doctor will perform a physical examination and order blood tests to measure your hormone levels; we collectively call these labs thyroid function tests (TFTs) – TSH, free T4, total T3.

TSH test: TSH is a hormone released from your pituitary gland when there is not enough thyroid hormone in the system. TSH will be low if there is too much thyroid hormone (hyperthyroidism).

Free T4 and total T3 test: T3 and T4 are thyroid hormones and these will be high in hyperthyroidism.

It is important to know that biotin can interfere with the testing of thyroid function in many labs, and you should check with your doctor to see if you should stop your biotin supplement beforehand.

To determine the type of hyperthyroidism you have, your doctor may do different tests: 

  • A thyrotropin receptor antibody test (TRAb) which can be elevated in Graves disease.
  • A radioactive iodine uptake test to measure how much iodine your thyroid collects from the bloodstream (certain conditions have low uptake and others have high uptake) 
  • A thyroid ultrasound to look at size of the thyroid and if there nodules 


How is hyperthyroidism treated?

Treatment for hyperthyroidism will depend on its cause, your age and physical condition, and how serious your thyroid problem is. Sometimes, only observation is needed, but most of the time, some treatment is helpful.  Available treatments include:

  • Antithyroid medications. These drugs lower the amount of hormone the thyroid gland makes. The preferred drug is methimazole. For pregnant or breastfeeding women, propylthiouracil (PTU) may be preferred. Because PTU has been linked to greater side effects, it is not used routinely outside of pregnancy. Both of these drugs control, but may not cure, hyperthyroidism. These medications have important side effects that should be discussed with your doctor.
  • Radioactive iodine.This treatment will cure the thyroid problem, but usually leads to permanent destruction of the thyroid. You will likely need to take thyroid hormone pills for the rest of your life to provide normal hormone levels. This treatment is generally tolerated very well, but can worsen Graves eye disease if it is present.
  • Surgery. Surgical removal of the thyroid gland (thyroidectomy) is a permanent solution, but not usually preferred, because of the risk of damage to the nearby parathyroid glands (which control calcium levels in the body) and to the nerves to the larynx (voicebox). Doctors may recommend surgery when either antithyroid medication or radioactive iodine therapy would not be appropriate.
  • Beta blockers. These drugs (such as atenolol) do not lower thyroid hormone levels, but can control many troubling symptoms, especially rapid heart rate, trembling, and anxiety.
  • Some additional medications can be used with severe hyperthyroidism 
  • If hyperthyroidism is caused by too much thyroid (levothyroxine) medication, then your doctor may have you decrease your dose.  
All of these therapies have risks. Your doctor will work with you to decide which treatment option is best for you.

What should you do if you think you might have thyroid problems?

Many of the signs and symptoms of hyperthyroidism may occur in other conditions. An endocrinologist, a specialist in hormone-related conditions, can help diagnose and treat hyperthyroidism. If you have ever been treated for hyperthyroidism, or are currently being treated, see your doctor regularly so that your condition can be monitored. It is important to ensure that your thyroid hormone levels are normal and that you're getting enough calcium to keep your bones strong.

Questions to ask your doctor

  • Do I have hyperthyroidism?
  • What is the cause of my hyperthyroidism? 
  • What treatment do I need for hyperthyroidism? 
  • What are the risks and benefits of each of my treatment options?
  • How often do I need monitoring for each type of treatment? 
  • What should I do about my hyperthyroidism if I want to get pregnant? 
  • What else can I do to stay healthy?
  • Should I see an endocrinologist for my care? 
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The Hormone Health Network is the public education affiliate of the Endocrine Society dedicated to helping both patients and doctors find information on the prevention, treatment and cure of hormone-related conditions.

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