Understanding Overactive Thyroid (Hyperthyroidism)

Medically reviewed by Kelly Wood, MD

An overactive thyroid (hyperthyroidism) is when the thyroid gland makes more hormones than you need. The two main hormones secreted by the thyroid are thyroxine (T4) and triiodothyronine (T3).

Thyroid-stimulating hormone (TSH), which comes from the pituitary gland, regulates these hormones. Having too many thyroid hormones can affect your body in multiple ways.

This article covers the symptoms, causes, and treatment of an overactive thyroid.

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Common Symptoms With Overactive Thyroid

Thyroid hormones affect the way your body uses energy. When you have more thyroid hormones than you need, it speeds up many body functions, which can cause various symptoms.

Weight Loss and Increased Appetite

An overactive thyroid speeds up metabolism, so you burn calories faster. It also boosts your appetite. If you take in more calories, you might not lose weight. The more severe the hyperthyroidism, the greater the weight loss.

Rapid or Irregular Heartbeat

You may notice your heart beating faster when you're physically active or at rest. Thyroid hormones have a significant impact on heart function and structure. Hyperthyroidism increases heart rate and can cause palpitations and abnormal heart rhythms, including atrial fibrillation (A-fib).

Mood Swings

Thyroid disease can affect your mood and cause mood swings, as well as the following:

  • Nervousness

  • Irritability

  • Anxiety

  • Nervous energy that makes it hard to sit still

You may be more prone to mood swings if you have other symptoms, such as sleep problems and fatigue.

Shakiness and Trembling

You might have trouble keeping a steady hand. Overstimulated nerves can lead to shaking, twitching, and trembling, which are common symptoms of hyperthyroidism. About 75% of people with an overactive thyroid have tremors, which may affect the hands and arms.

Sleep Problems and Fatigue

Hyperthyroidism is a well-known cause of sleep dysfunction and is associated with:

  • Taking longer to fall asleep

  • Trouble staying asleep

  • Excessive daytime sleepiness

  • Insomnia

Sleep problems might be worse if you also have symptoms such as tremors, nervousness, or anxiety. Combining a sped-up metabolism and sleep problems can lead to ongoing fatigue.

Sweating, Heat Intolerance

When your metabolism speeds up, your body temperature rises, which can lead to:

Bowel Changes

When your digestive system speeds up, it can lead to frequent loose bowel movements or diarrhea.

Bulging Eyes

In Graves' disease, an excess of thyroid hormones can cause the eyelids to retract, so your eyes appear to bulge. Other eye symptoms can include puffiness, watering, and double vision.


Hyperthyroidism can cause a goiter, when your thyroid gland enlarges enough to bulge out of the side of your neck.

Symptom Variations

Most people don't have all symptoms; some may be more severe than others. Other signs and symptoms of overactive thyroid are:

Hyperthyroidism symptoms in females can include lighter or missed periods and trouble getting pregnant.

In older adults, an overactive thyroid can look a lot like depression. Older adults are also more likely to experience loss of appetite and social withdrawal.


Thyrotoxicosis is an excessive release of thyroid hormones. A thyroid storm is severe thyrotoxicosis. This is a potentially life-threatening event that requires immediate medical treatment. Other severe overactive thyroid symptoms include:

Asymptomatic and Undiagnosed Overactive Thyroid

Some people have thyroid dysfunction but no apparent symptoms. Without treatment, an overactive thyroid can lead to potentially severe complications involving the heart, eyes, and pregnancy. It can also lead to a thyroid storm.


Many signs and symptoms of hyperthyroidism can be due to other issues, so it's important to seek a diagnosis. A healthcare provider can use TSH, T3, T4, and thyroid antibody blood tests to check for high thyroid levels. Other diagnostic testing may include physical exam and imaging tests.

Why Do Some People Have an Overactive Thyroid?

The most common cause of hyperthyroidism is Graves' disease, an autoimmune disorder in which the immune system attacks a healthy thyroid. Other causes include:

Hyperthyroidism is more common in females and people older than 60. Other risk factors include:

Secondary Complications of Overactive Thyroid

Complications of an overactive thyroid may include:

  • Blood clots, stroke, or heart failure due to irregular heartbeat

  • Pain, ulcerations, or vision loss due to Graves' ophthalmopathy, an autoimmune condition

  • Thinning, brittle bones (osteoporosis) due to poor calcium absorption

During pregnancy, your baby depends on thyroid hormones for brain and nervous system development. Untreated hyperthyroidism in pregnancy can cause:

Does Treatment Reverse an Overactive Thyroid?

Treatment may be able to get your thyroid levels back under control. Eventually, you may be able to reduce, then stop taking medication. However, many people will need to take medicine longer or for life.

Overactive Thyroid Medications

Antithyroid medicines, such as Tapazole (methimazole) and PTU (propylthiouracil), cause the thyroid to produce fewer hormones. You may have to take them for one or two years or longer.

Beta-blockers (metoprolol or propranolol) don't treat hyperthyroidism. They can help manage nervousness, rapid heartbeat, and hand tremors.

Surgery and Treatment for Severe Overactive Thyroid Complications

You may need surgery to remove the thyroid gland. Another option is to destroy the thyroid with radioactive iodine.

Because surgery and radioactive iodine stop the production of thyroid hormones, you'll have hypothyroidism. You'll need to take synthetic thyroid hormones for the rest of your life.

How to Manage Overactive Thyroid Symptoms

While there is no hyperthyroidism diet, avoiding certain foods may be helpful, especially those containing large amounts of iodine. These foods can cause the thyroid to produce too much thyroid hormone. A healthcare provider may recommend that you avoid foods such as:

  • Iodized salt

  • Dietary or prenatal supplements containing iodine

  • Foods fortified with iodine, including milk products

  • Seaweeds and saltwater fish

Certain herbs and dietary supplements may help, but because some can interfere with medication, it's important to discuss this with a provider first.

Exercise is important to overall health and may help with some symptoms. An overactive thyroid affects the heart and cardiovascular system. This can put too much strain on the heart. Consult a healthcare provider before starting a new or more strenuous exercise routine.


Hyperthyroidism is when the thyroid releases more hormones than you need, which increases metabolism and affects your body in many ways. Symptoms can include weight loss, rapid heartbeat, and bulging eyes. Heart problems, eye problems, and osteoporosis are potential complications. It's particularly dangerous during pregnancy.

Antithyroid medicines can help get your hormones back in balance. But in some cases, you may need surgery to remove the thyroid gland. Radioactive iodine therapy to stop the thyroid from working is another option.

Read the original article on Verywell Health.