What is hyperthyroidism?
Hyperthyroidism is a condition in which the thyroid gland located at the front of your neck produces too much thyroid hormone. Thyroid hormone regulates your body’s energy and metabolism. An overactive thyroid causes every function of your body to speed up. This overactivity is often referred to as an overactive thyroid or overactive thyroid gland.
What causes hyperthyroidism?
Hyperthyroidism has several causes:
- Graves’ disease. This is the most common cause of hyperthyroidism. It occurs when your immune system mistakenly attacks your thyroid gland, causing it to overproduce thyroid hormone.
- Thyroid nodules. Nodules are lumps that develop on your thyroid gland. Some nodules may overproduce thyroid hormone, causing hyperthyroidism.
- Thyroiditis. Thyroiditis is inflammation of your thyroid gland. Types of thyroiditis that may lead to hyperthyroidism include subacute thyroiditis and postpartum thyroiditis.
- Excess iodine intake. Consuming too much iodine may cause your thyroid gland to overproduce thyroid hormone.
- Medications. The medication amiodarone, used to treat heart rhythm disorders, may affect thyroid function and cause hyperthyroidism.
Less common causes of hyperthyroidism include:
- A pituitary disorder.
- Taking too much thyroid hormone medication.
- A benign tumor of the testes or ovaries.
- Pregnancy.
- Cancer of the testes, ovaries, or thyroid.
In about 10% of people with hyperthyroidism, the condition may occur for no obvious reason.
What are the symptoms of hyperthyroidism?
Hyperthyroidism speeds up your body’s metabolism significantly, so signs and symptoms can be wide-ranging:
- Sudden weight loss. Hyperthyroidism accelerates your metabolism, so despite a good appetite, you may experience significant weight loss. You may lose weight even if you eat more.
- Rapid heartbeat. Your heart rate may increase from 100 beats per minute to 180 or more beats per minute. Your heart may pound, and you may have heart palpitations — a sensation that your heart is skipping beats.
- Increased appetite. You may feel hungry all the time, even after you eat.
- Nervousness, anxiety and irritability. Hyperthyroidism may make you feel jumpy, wired and irritable. You may also feel anxious and sleep poorly.
- Trembling hands. Your hands may shake slightly because of fast metabolism and circulating hormones.
- Sweating and heat intolerance. You may sweat a lot and feel uncomfortably warm.
- Hair loss. Temporary hair loss often occurs on your scalp and sometimes your eyebrows.
- Muscle weakness. Weakness occurs early on in thighs and upper arms.
- Shortness of breath and fatigue. You may feel short of breath and tired even with minimal exertion.
- More frequent bowel movements. You may develop diarrhea and frequent bowel movements as food moves more rapidly through your intestines.
- Menstrual changes. In women, menstrual flow may lighten and menstrual periods may occur less often.
- Thyroid gland enlargement. Your thyroid gland located at the front of your neck may visibly enlarge as it becomes overactive (goiter).
- Eye changes. Rarely, you may experience vision problems, irritation or light sensitivity, or your eyes may protrude.
When to see a doctor
See your doctor if you have any of the signs or symptoms common to hyperthyroidism. Many signs and symptoms of hyperthyroidism are similar to those caused by other conditions.
Seek immediate medical care if you develop:
- Racing heartbeat
- Chest pain
- Shortness of breath
- Fainting
- Vision changes
- Persistent nausea and vomiting
Complications of hyperthyroidism
Hyperthyroidism can accelerate your body’s metabolism significantly, causing a number of complications:
- Irregular heartbeat. Rapid heart rate and irregular heartbeat can develop. Atrial fibrillation — an irregular and rapid heart rate — is the most common heart complication. However, this and other heart complications improve once hyperthyroidism is treated.
- Heart failure. A common, potentially serious complication is heart failure caused by untreated hyperthyroidism and dangerous heart rhythms.
- Brittle bones. Untreated hyperthyroidism depletes calcium levels and accelerates bone turnover, increasing your risk of osteoporosis and bone fractures later.
- Thyroid storm. Rarely, untreated hyperthyroidism may progress to thyroid storm. This is a sudden and severe worsening of hyperthyroidism symptoms that may result in fever, fainting, dehydration, confusion, shock and even death.
When to see a doctor
Early diagnosis and treatment of hyperthyroidism are important to prevent complications. Talk to your doctor if you think you have signs or symptoms of an overactive thyroid gland.
Tests and diagnosis
To determine if you have hyperthyroidism, your doctor will likely do a physical exam and ask detailed questions about your symptoms. Your doctor may also order blood tests to check for high levels of thyroid hormones as well as low levels of pituitary thyroid stimulating hormone (TSH), which normally signals your thyroid gland to slow production of thyroid hormones.
Your doctor may order additional tests to confirm the cause of your hyperthyroidism. These may include:
- Radioactive iodine uptake test. This measures how much iodine your thyroid gland absorbs from your bloodstream. People with hyperthyroidism absorb much more iodine than healthy people do.
- Thyroid scan. Using a small amount of radioactive material, a thyroid scan takes pictures of your thyroid when it’s most active — about 24 hours after you swallow the radioactive iodine. The images show areas of inflammation and nodules.
- Ultrasound. An ultrasound uses sound waves to create an image of the gland to identify inflammation and enlargement or nodules.
Common causes of hyperthyroidism and related tests
| Cause | Related tests |
|---|---|
| Graves’ disease | Blood tests that measure thyroid-stimulating immunoglobulin (TSI) antibodies |
| Thyroid nodule | Ultrasound, thyroid scan, or fine needle aspiration of the nodule |
| Thyroiditis | Blood tests, thyroid scan |
| Excess iodine intake | 24-hour urine sample to estimate iodine content |
| Medications, supplements | Discussion of all current prescriptions, supplements and vitamins |
Treatment
Several effective treatments are available for hyperthyroidism, each aimed at blocking your thyroid gland’s ability to produce excess hormones.
Medications
Medications commonly used to treat hyperthyroidism include:
- Anti-thyroid medications. Methimazole (Tapazole) and propylthiouracil (PTU) interfere with thyroid hormone production. They block the thyroid’s ability to take in iodine, which is needed for thyroid hormone production.
- Beta blockers. Drugs like propranolol (Inderal LA, InnoPran XL) are used to quickly bring rapid heart rate under control until other hyperthyroidism treatments become effective. Potential side effects include fatigue, lethargy, impaired thinking and other heart problems.
Radioactive iodine
Radioactive iodine involves taking radioactive iodine (I-131) in pill form. Over weeks to months, the radioactive material accumulates in your thyroid gland and destroys thyroid cells. Radioactive iodine has been safely used for more than 70 years for hyperthyroidism treatment.
Surgery (thyroidectomy)
Removing all or most of your thyroid gland is an alternative treatment for hyperthyroidism. Normally, hyperthyroidism treatment with radioactive iodine is the preferred treatment option, but thyroidectomy may be recommended if:
- Your thyroid gland is substantially enlarged (goiter)
- You can’t tolerate anti-thyroid drugs
- Radioactive iodine isn’t an option during pregnancy
- You have compressive symptoms or very severe hyperthyroidism
Home care and lifestyle changes
Self-care steps that may help improve your hyperthyroidism symptoms include:
- Eat more frequent, smaller meals. This may reduce appetite and potential weight loss.
- Temporarily avoid calcium-rich foods that may interfere with hyperthyroidism treatment. These include milk, yogurt, cheese, ice cream, cereals, oatmeal, nuts, beans and some vegetables.
- Protect yourself from excessive heat and humidity while your metabolism is revved up. Stay in air conditioning when possible and drink cold beverages.
- Limit stress and get adequate rest and sleep since stress and fatigue can worsen hyperthyroid symptoms.
Tell your doctor about any supplements or over-the-counter products you take. High-dose biotin supplements, for example, may interfere with thyroid lab test results.
When to follow up with your doctor
It’s important to follow up regularly after you begin treatment for hyperthyroidism to:
- Evaluate your thyroid function with repeat blood tests.
- Monitor your heart rate and rhythm.
- Adjust your medication dosages as needed.
- Schedule radioactive iodine treatment if anti-thyroid medications aren’t effective.
- Evaluate the need for thyroid surgery if indicated.
- Monitor for improvement in your signs and symptoms.
Left untreated, hyperthyroidism can lead to serious complications. But with proper treatment, hyperthyroidism can be well-controlled.
Conclusion
Hyperthyroidism is a condition in which the thyroid gland becomes overactive and produces too much thyroid hormone. This causes metabolism to speed up significantly. Symptoms may include sudden weight loss, rapid heartbeat, hand tremors, anxiety, and more. Graves’ disease is the most common cause. Early diagnosis and treatment are important to prevent complications like irregular heartbeat, heart failure, brittle bones, and thyroid storm. Treatment options include anti-thyroid medications, radioactive iodine, and thyroid surgery. With proper management, hyperthyroidism symptoms can be controlled.