Hyperthyroidism, also known as overactive thyroid, is a condition where the thyroid gland produces more thyroid hormones than your body needs.
The thyroid is a butterfly-shaped gland in the front of your neck (below the Adam’s apple in men) that releases the hormones T3 (triiodothyronine) and T4 (thyroxine).
An overactive thyroid producing too much of these hormones causes an imbalance in your body, which can lead to symptoms and complications when left untreated.
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Hypothyroidism and hyperthyroidism are both conditions where the thyroid doesn’t work correctly. In hypothyroidism, the thyroid is underactive and produces too little thyroid hormone, while the opposite occurs in hyperthyroidism.
Hyperthyroidism affects around 1.3%¹ (4–5% among older females) of people in the US, while hypothyroidism only affects around one in 300.²
The symptoms of hyperthyroidism can be similar to other health conditions, making it tricky to identify in some cases.
Here are some of the symptoms to watch out for:
Shortness of breath
Nausea and vomiting
Irregular or rapid heartbeat
Anxiety and nervousness
Research has also linked the following symptoms with hyperthyroidism:
It’s common for people with hyperthyroidism to experience hair loss. This symptom isn’t specific to your head; you may also lose hair from different parts of your body.
According to a study³ of 1,232 patients over 25 months, researchers found a link between urticaria (hives) and vitiligo (white patches on the skin) and hair loss and thyroid dysfunction.
Unexpected and unintentional weight loss
Hypothyroidism is associated with weight gain, while hyperthyroidism is linked to weight loss. According to one study,⁴ participants with higher levels of T3 and T4 hormone experienced more significant weight loss than people with healthy thyroids.
Unexpected weight loss in people with hyperthyroidism occurs because the body burns energy faster than it would normally.
Large thyroid gland or a goiter
A “goiter” is an abnormal growth in your thyroid gland that can occur with hyperthyroidism, hypothyroidism, or euthyroidism (when the thyroid gland produces the right amount of hormone).
Irregular menstrual cycle
Women with hyperthyroidism may experience an irregular menstrual cycle, with some cases causing the cycle to stop completely.
According to a study,⁵ the prevalence of irregular menstrual cycles in hyperthyroidism patients used to be as high as 65%, but earlier detection and treatment has lowered this figure to 21.5%.
Speak to your doctor if you think you might have hyperthyroidism. This will enable you to get diagnosed and receive treatment as soon as possible. Your doctor may refer you to an endocrinologist (a hormone specialist) for testing, diagnosis, and treatment.
Even if you don’t have hyperthyroidism, you should discuss your symptoms with a medical professional and find out what’s causing them.
Physical exam and clinical findings
Your doctor will ask you about your symptoms, personal medical history, and family medical history. They will also carry out a physical exam and will feel around your neck for a goiter.
Your doctor or endocrinologist will carry out biochemical testing to measure:
Thyroid-stimulating hormone (TSH)
The results of these tests may show you have hyperthyroidism.
Image tests and scanning
Once hyperthyroidism is confirmed with blood tests, your doctor or endocrinologist may use a radioactive iodine uptake test (RAIU) to work out what’s causing your hyperthyroidism and determine the best treatment.
A color-flow Doppler ultrasound could also help you get a diagnosis, especially when an RAIU scan is unsuitable; for example, during pregnancy, while breastfeeding, or because of allergies.
Some people are more susceptible to hyperthyroidism than others. These risk factors could increase your chance of developing the condition.
Although it’s possible to develop hyperthyroidism at any age, one study⁶ found the risk of developing the condition peaks in your twenties and thirties. However, people aged 60 and above make up 10–15%⁶ of all hyperthyroidism cases.
Women are more at risk of developing hyperthyroidism than men, while being an older woman increases your risk substantially.
A study⁷ of 8,532 males and 5,323 females found that female participants were more likely to develop thyroid dysfunction than male participants, and that risk further increased with age.
Family history of hyperthyroidism
Your chance of being diagnosed is higher if you have family members with hyperthyroidism.
To ensure early detection and treatment, discuss your family’s medical history and keep a close eye on symptoms if the condition is in your family.
Other health conditions
Some health conditions can increase your risk of developing hyperthyroidism, including:
Diabetes (type 1 or type 2)
Primary adrenal insufficiency
High iodine intake
Consuming too much iodine can cause you to develop hyperthyroidism or other conditions like goiter, hypothyroidism, and thyroid autoimmunity.
Research⁸ shows excess iodine intake can occur when you consume one or more of the following:
Drinking water (this is unlikely as iodine levels are typically low in drinking water)
Animal milk rich in iodine
Iodine-containing dietary supplements
Identifying the signs and symptoms of hyperthyroidism early can help you get treatment, but complications can occur if the condition goes untreated for a long time.
Hyperthyroidism complications include:
Hyperthyroidism is known to cause thinning bones. Severe, untreated cases can increase the likelihood of high bone turnover osteoporosis.⁹
A study⁹ found thyroid hormones play an important role in bone health, maturity, and strength, but too much thyroid hormone in the body increases the risk of bone disease.
Another study¹⁰ on 38 premenopausal women with newly diagnosed hyperthyroidism found a decrease in bone mineral density in the cortical layer of the neck of the femur (the section of bone that joins the head of the femur with the long section). The prevalence of osteoporosis was also found to be higher in women with a history of hyperthyroidism.
Although the exact association between fertility issues and hyperthyroidism hasn’t yet been defined or established, research⁵ has reported a 0.9–5.8% prevalence of primary or secondary infertility linked with hyperthyroidism.
A study¹¹ found an association between hyperthyroidism and early pregnancy loss if the condition is not treated quickly.
Other pregnancy complications due to untreated hyperthyroidism include:
Intrauterine growth restriction (IUGR)
Low birth weight
Atrial fibrillation (irregular heartbeat)
Around 10–15%¹² of people with hyperthyroidism have an irregular heartbeat, and the percentage increases with age.
Atrial fibrillation complications include:
Blood clots leading to stroke
Other heart issues
Every patient is different, so hyperthyroidism treatment may not be the same for everyone. Your doctor can discuss options with you and suggest a suitable treatment.
Hyperthyroidism treatment options include the following:
Two common types of medication can be taken to manage hyperthyroidism symptoms: antithyroid drugs and beta-adrenergic blockers.
While taking these medications can control the condition and its symptoms, they don’t cure hyperthyroidism.
Antithyroid drugs available in the US include:
Propylthiouracil (preferred for use during pregnancy, especially in the first three months)
Beta-adrenergic blockers for hyperthyroidism include:
Radioiodine therapy is an effective treatment used to destroy thyroid cells through radiation. It generally causes few side effects (typically only sore throat and neck tenderness).
It is administered orally and is safe to take at home in most cases.
Thyroid surgery can be an effective treatment for hyperthyroidism. A surgeon will remove your whole thyroid or part of it, and you may need to take thyroid hormone medication throughout your life.
If you’re aged 60 or older, your risk of hyperthyroidism is higher but your symptoms may not be noticeable. Stay in regular contact with your doctor to discuss any concerns.
If you have one or more risk factors for hyperthyroidism or you have any symptoms, such as neck swelling or unintentional weight loss, tell your doctor so they can make a diagnosis and provide a suitable treatment plan.
Never start new treatment without consulting your doctor first.
Hyperthyroidism symptoms can be similar to other conditions, making it tricky to diagnose in some cases. However, you should speak to your doctor if you notice any of the following symptoms:
Irregular menstrual cycle
Unexplained weight loss
Goiter (abnormal growth in the thyroid gland)
Being female and over 60 are significant risk factors for hyperthyroidism, especially if it runs in your family.
If you think you might have hyperthyroidism, discuss your concerns with your doctor immediately. They can work with you closely to identify what’s causing your symptoms and recommend a suitable treatment plan.
Hyperthyroidism treatment often includes medications, surgery, or radioiodine therapy. Untreated hyperthyroidism can cause many serious health complications, including stroke, heart problems, thinning bones, fertility issues, and pregnancy complications.
Disorders that cause hyperthyroidism | Up To Date
Hypothyroidism: An update (2012)
Hyperthyroidism (Overactive thyroid) | (NIDDK) National Institute of Diabetes and Digestive and Kidney Diseases