What You Need To Know About Hyperthyroidism

What is hyperthyroidism?

Hyperthyroidism or overactive thyroid occurs when your thyroid gland makes more thyroid hormones than your body needs. This excess hormone effectively increases the metabolism in all your cells. Your thyroid sits at the front of your throat.

Since the hormones produced by your thyroid regulate your metabolism, hyperthyroidism can affect nearly every function of your body. For example, hyperthyroidism can affect breathing, digestion, weight, and mood. If untreated, this condition can cause serious medical issues, including:

  • A rapid or irregular heartbeat

  • Bone issues, including osteoporosis

  • Complications during pregnancy

  • Fertility problems in females

  • An autoimmune disease called Graves' ophthalmopathy, also known as thyroid eye disease (TED)

What does your thyroid do?

Like other glands in your body, the thyroid creates and releases substances that help your body perform specific functions.

Your thyroid gland produces three hormones:

  • Triiodothyronine (T3)

  • Tetraiodothyronine (thyroxine or T4)

  • Calcitonin

The hormones produced by the thyroid play a significant role in the metabolism, growth, and development of virtually every cell and tissue in the human body. Thyroid hormones affect nearly all body functions, including cardiac output, resting heart rate, basal metabolic rate or BMR, and resting respiratory rate.

Other related conditions


Thyroid disorders are common, and anybody can be affected, including men and women of all ages and even children and babies. Over 12 percent of Americans will develop a thyroid condition during their lifetime, with nearly 60 percent unaware of their condition.¹

Hyperthyroidism is a condition that most commonly affects women and people over 60. Females are 10 times more likely to have hyperthyroidism than males.²

You are more at risk of hyperthyroidism if you have a family history of thyroid disease or other health problems, such as anemia, diabetes, or Addison's disease.

Your risks are also increased if you:

  • Eat foods rich in iodine or take medication containing iodine 

  • Smoke or use nicotine products

  • Have been pregnant within the past six months

  1. General information/press room | American Thyroid Association

  2. Hyperthyroidism (overactive thyroid) | NIH: National Institute of Diabetes and Digestive and Kidney Diseases


If you have hyperthyroidism, it can cause your bodily functions to speed up.

Hyperthyroidism can increase heart rate and cause anxiousness, nervousness, or irritability.

Your symptoms may include more frequent bowel movements or diarrhea, and you may lose weight despite having an increased appetite and eating well.

In addition, if you're female, hyperthyroidism affects your menstrual cycle by causing your flow to lighten or periods to occur less often.

Common symptoms of hyperthyroidism include:

  • Increased sweating

  • Hand tremors

  • Difficulty sleeping

  • Thinning of skin

  • Hair loss and changes in hair texture that make it brittle

  • Muscle weakness, especially upper arms and thighs

Since hyperthyroidism increases your metabolism, it's not surprising that many individuals initially experience increased energy.

However, hyperthyroidism wears you out as the condition continues, and feeling tired is very common.

Hyperthyroidism typically starts slowly, but often in some young patients, signs, and symptoms appear abruptly.  Early signs and symptoms are often mistaken for simple nervousness due to stress.


Several conditions can cause hyperthyroidism.

They fall into three broad categories:

  • Excess production of thyroid hormone within the gland

  • Processes that inflame or destroy thyroid tissue

  • Excess production of thyroid hormone from an external source

Excess production of thyroid hormone in the gland

Graves’ disease

The most common cause of hyperthyroidism, particularly in young women. Graves’ disease is caused by your body producing an antibody that stimulates excess thyroid hormone production and release.

Thyroid nodules

Growths in your thyroid (nodules) are usually benign but may grow and cause the thyroid to become overactive and emit excess thyroid hormone. Thyroid nodules are common in older adults.

Excess iodine intake

Iodine is commonly found in some medications and cough syrups, as well as in seaweed and seaweed-based supplements.


Certain cancers produce hormones that can stimulate the thyroid to produce excess hormones (rare).

Destruction of thyroid tissue


Thyroid inflammation from a viral infection or immune system problem. The condition can cause your thyroid to leak stored thyroid hormones. Thyroiditis is also caused by certain medications or thyroid radiation.

External sources of thyroid hormone

Thyroid hormone replacement (HRT)

Excessive thyroid hormone replacement for an underactive thyroid can cause complications.

Ovarian cancer

Certain cancers of the ovaries can produce thyroid hormones.

What's the difference between hyperthyroidism and hypothyroidism?

Hyperthyroidism is an overactive thyroid. If you have hypothyroidism, you have an underactive thyroid.

Hypothyroidism is more common in the United States than hyperthyroidism. However, it's not uncommon for a person to have an underactive thyroid and then an overactive thyroid, or vice versa.

To properly treat a thyroid condition, it's vital to find a skilled and knowledgeable doctor specializing in thyroid disorders (typically an endocrinologist).

If you have hyperthyroidism, you may feel like you have more energy. Still, the increased activity of your body's cells and organs may cause issues, including unexplained weight loss, feelings of anxiousness, increased heart rate, or faster digestion resulting in diarrhea.

If you have an underactive thyroid or hypothyroidism, your thyroid does not produce enough hormones. As a result, your metabolism slows down, leaving you feeling tired and may cause weight gain. In addition, the condition affects all of your body functions and can slow your heart rate, cause your digestive system to work sluggishly, and lead to constipation.

How is an overactive thyroid diagnosed?

If your doctor suspects you have hyperthyroidism, they will usually start by asking about your medical history and looking for symptoms. Along with reviewing your history and conducting a physical exam, they will usually request bloodwork and imaging tests before making a diagnosis. They may also recommend consulting an endocrinologist —  a specialist in hormone-related diseases and conditions.

What does thyroid testing involve?

Because hyperthyroidism can be challenging to identify, your doctor will perform and order several tests to check your thyroid activity.

Physical exam

During your physical exam, your doctor may ask questions about your medical history and gently inspect your thyroid through your skin to see if there is swelling of the thyroid (goiter). A goiter is a sign of an enlarged thyroid and can be bumpy or tender. They will also feel your skin to see if it is warm and moist and may ask you to extend your hands to look for a tremor. Next, your doctor will check your pulse and use a stethoscope to listen to your heart for an irregular or rapid heartbeat. Finally, they may check your eyes for swelling, redness, bulging, which can occur with Graves’ Disease.


Checking for hyperthyroidism involves blood tests that measure your level of thyroid hormones.

In addition to checking the levels of thyroid hormones in your blood, blood tests may also measure the level of thyroid-stimulating hormone, also called TSH. TSH is a hormone produced by the pituitary gland and stimulates the thyroid.

If you have hyperthyroidism, thyroid hormone levels will be higher than expected, while thyroid-stimulating hormone is below average.

Your bloodwork may also include tests to measure thyroid antibodies in your system. Thyroid antibodies go into production when your immune system mistakenly attacks the thyroid gland. Your doctor usually orders thyroid antibody tests if the results of other blood tests suggest thyroid disease.

Imaging tests

Your doctor or endocrinologist may also order one or more imaging tests to find the cause of your thyroid disease and diagnose the condition.

Imaging tests are usually done in your doctor’s office, outpatient facility, or hospital. Imaging tests are performed by a radiologist, a doctor specializing in medical imaging.

The radiologist will review the images and then send a report to your physician to discuss with you.


An ultrasound is a standard procedure used to look for and more closely examine thyroid nodules. This imaging test can help your doctor determine if the nodules are likely to be cancerous.

During an ultrasound, you are lying on an exam table while a technician runs a device called a transducer over your neck. The transducer creates an image of your thyroid by bouncing sound waves off your neck. The procedure is painless and usually takes around 30 minutes to complete.

Thyroid scan

A thyroid scan enables your doctor to inspect your thyroid gland’s position, size, and shape—a small amount of radioactive iodine checks for thyroid nodules during this test. The week before your scan, your doctor may ask you to avoid foods high in iodine or medications containing iodine.

For the scan, a technician will inject a small amount of radioactive iodine into your vein, or they may ask you to swallow the substance in liquid or capsule form. The scan typically occurs about 30 minutes after the injection or up to 24 hours after taking a capsule. Once absorbed, a special camera takes pictures of your thyroid while you lie on an exam table.

Radioactive iodine causes thyroid nodules to show up clearly in the pictures, and if it shows up throughout the entire thyroid gland, it could indicate Graves’ disease. While a thyroid scan is safe and uses only a tiny amount of radioactive material, you should not have this test if you are pregnant or breastfeeding.

Radioactive iodine uptake test

A radioactive iodine uptake test, also known as a thyroid uptake test, helps check thyroid function and determine the cause of hyperthyroidism. The test takes only a few minutes and is sometimes performed simultaneously with a thyroid scan.

When the test begins, you will swallow a small amount of radioactive iodine in liquid or capsule form. During the test, a technician will have you sit in a chair while they place a device known as a gamma probe in front of the neck, near your thyroid gland.

The probe measures the amount of radioactive iodine your thyroid takes up from your blood, with measurements typically taken 4 to 6 hours after you swallow the radioactive iodine and again at 24 hours.

Is hyperthyroidism commonly misdiagnosed?

In the early stages, hyperthyroidism may have no symptoms or vague symptoms, which usually develop gradually. As a result, overactive thyroid is often misdiagnosed or mistaken for other health problems.

Hyperthyroidism can affect your mood and cause anxiety. Typically, the more severe your hyperthyroidism, the more influential the mood changes. As a result, people get misdiagnosed with panic attacks or high anxiety. In addition, anti-depressants will not improve the symptoms.

Thyroid function has a significant influence on a woman's reproductive system. Abnormally high levels of thyroid hormones can cause very light menstrual flow, irregular menstrual cycles, or missing periods. Some of these symptoms, including lack of menstruation, hot flashes, inability to sleep, and mood swings, can easily be mistaken for menopause.

To further complicate the diagnosis, a thyroid disorder can sometimes cause early menopause. However, with proper treatment, symptoms of early menopause can be lessened or prevented.


Whatever the underlying cause of your hyperthyroidism, there are effective treatments that can manage and control your symptoms.

Anti-thyroid medications

Anti-thyroid medications gradually reduce symptoms of hyperthyroidism by blocking your thyroid's ability to produce hormones. They offer rapid control of your thyroid, with symptoms usually improving within several weeks or months.


Beta-blockers work to block the action of your thyroid hormones. Beta-blockers are often combined with other forms of treatment long-term. Beta-blockers don't affect your hormone levels but help control hyperthyroidism symptoms such as rapid heartbeat, nervousness, and shakiness.

Radioactive iodine

Radioactive iodine is an oral medication absorbed by your overactive thyroid cells. The substance damages these cells, causing your thyroid to shrink and thyroid hormone levels to go down in a few weeks.

The amount of radiation in this medication is different from that used in imaging procedures and usually will permanently destroy the thyroid, effectively curing your hyperthyroidism. Since this treatment destroys the thyroid, most people who receive it have to take thyroid hormone drugs for the rest of their lives to maintain normal hormone levels.


Your doctor may elect to remove your thyroid through surgery. Surgery can eliminate your hyperthyroidism but usually causes an underactive thyroid, requiring lifelong thyroid supplements to normalize levels.


There aren't any specific steps to eliminate the risk of thyroid disease. However, there are ways to lower your risk (or manage your condition if you're diagnosed with hyperthyroidism).

Undiagnosed hyperthyroidism increases the risk of developing a variety of other medical conditions. Therefore, it's essential to be aware of thyroid disease and pay attention to any unusual symptoms.

You can reduce your risk by avoiding alcohol and products containing caffeine. If you're using tobacco products, consider quitting and, if possible, exercise for 30 minutes a day, five days a week.

You could also talk to a dietitian about the suitability of eliminating dairy, soy, preservatives, and other food additives. They may recommend avoiding processed foods, like white bread, pasta, and sugar, and increasing the amount of antioxidant-rich foods you eat, such as fruits and vegetables, in your diet.

Doctors & specialists

Hyperthyroidism is treatable. If you're experiencing any of the above signs and symptoms, it's vital to see a healthcare professional so they can assess your condition and recommend treatment.

If you notice a lump, nodule, or other growth on your thyroid, a professional should examine it. You should also consult with your doctor if you are experiencing increased sweating, hand tremors, insomnia, weakness in your arm and leg muscles, or hair loss.

If you're experiencing severe symptoms, such as a high fever and fast heart rate, you should seek emergency treatment immediately.

You may be referred to an endocrinologist who specializes in hormone disorders.