Your thyroid gland plays an important role in your life. It supplies the hormones you need to build muscle, absorb nutrients, and regulate temperature. But what happens when your thyroid produces too many hormones?
Each year, millions of Americans suffer from an overactive thyroid. Trying to diagnose thyroid issues isn't always easy, as many of the symptoms of an overactive thyroid are shared by other conditions and diseases.
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Your thyroid gland is a small, butterfly-shaped organ in your neck that sits above your voice box and below your thyroid cartilage (also called your "Adam's apple").
The thyroid is a gland that is part of the endocrine system. You have glands throughout your body (e.g., pancreas, testis, ovaries, adrenal, etc.). Each one creates and secretes hormones to help regulate many processes, including your energy levels, metabolism, growth, mood, and stress levels.
Your endocrine system regulates virtually all biological processes in your body, including the development of your brain, your reproductive system, and your nervous system.
From blood sugar levels to feelings of joy and excitement, your endocrine system releases specialized hormones that play a massive role in your day-to-day life.
The human thyroid isn't perfect: sometimes various medical conditions, lifestyle choices, environmental factors, or genetic factors cause it to produce too many (or too few) hormones.
The most common thyroid disease is called hypothyroidism, which happens when your thyroid fails to produce enough thyroid hormones. Typically, hypothyroidism is caused by a deficiency in iodine or can temporarily present in 3 to 8% of women after childbirth.¹
When too many hormones are produced, it's called hyperthyroidism —sometimes referred to as having an "overactive" thyroid gland.
The three most common causes of hyperthyroidism are:
People with this autoimmune disorder produce too many hormone-stimulating antibodies, causing the thyroid to over-produce T3 and T4.
This condition is the most common cause of hyperthyroidism in the United States, affecting around 0.5% of men and 3% of women. Grave's disease is the cause of 60-80% of all hyperthyroidism cases.²
A toxic nodular or multinodular goiter
People with either a toxic nodular or multinodular goiter develop adenomas in their thyroid that produce too many thyroid hormones. These adenomas do not respond to signals from your thyroid or pituitary gland to stop producing hormones.
People with thyroiditis have an inflamed or swollen thyroid gland. A variety of conditions can cause thyroiditis, including postpartum physiological changes, viruses, bacteria, stress, or trauma.
While the vast majority of hyperthyroidism cases are caused by the conditions above, there are other causes, including:
Taking too many iodine supplements can cause temporary hyperthyroidism.
People with this autoimmune disorder often have their thyroid glands damaged by their own immune cells. Typically, this causes a lack of thyroid hormones (i.e., hypothyroidism). However, in rare cases, temporary hyperthyroidism is diagnosed.
This condition causes intense nausea and vomiting during pregnancy. Rarely, it can also cause temporary hyperthyroidism.
Cancerous tumors affecting the thyroid can cause both hyperthyroidism and hypothyroidism.
People with exogenous hyperthyroidism have hyperthyroidism caused by excessive ingestion of thyroid hormones, usually from medication for the treatment of thyroid cancer. However, a few cases have been shown to be caused by contaminated supplements.
Having too many thyroid hormones in your blood can cause many different symptoms, with the most common shown below.
However, there are also rare symptoms caused by infrequent and unique thyroid mechanisms that may not be listed. It's important to consult a healthcare professional with any questions you have about your symptoms.
The most common symptoms of hyperthyroidism include:
Anxiety or nervousness
High pulse rate (also called tachycardia)
Sensitivity to temperatures
Hand trembling or shaking (also called tremors)
Sensitivity to light
Less common symptoms
Symptoms that are less common (but not necessarily "rare") include:
Swollen thyroid gland
Missed menstrual periods
Protruding eyeballs (also called Graves' ophthalmopathy)
Shortness of breath (also called dyspnea)
Reddening and thickening of the skin (also called Graves' dermopathy)
Certain people are more susceptible to hyperthyroidism. Remember, having risk factors does not mean you have or will get hyperthyroidism, and most people with risk factors never develop the condition.
However, being aware of risk factors can help you make informed decisions, discuss potential symptoms with your doctor, and adapt any lifestyle choices that may put you at risk of developing hyperthyroidism in the future.
Hyperthyroidism and Graves’ disease are more common in people over 30 years old.³
Females are much more likely to develop hyperthyroidism, and Graves’ disease is more likely to occur in women rather than men. Women have a 3% risk of developing the disease during their lifetime, while men have a 0.5% risk.² Females can also develop postpartum hyperthyroidism.
The role of ethnicity in hyperthyroidism is poorly understood as there is conflicting data. For example, a recent pooled analysis of young adults in the United States suggests that non-Hispanic Black people are three times more likely⁴ to get thyrotoxicosis than non-Hispanic white people. Yet, a different pooled analysis in Brazil showed that non-Hispanic white people had the highest risk.⁵
Having an autoimmune disorder (such as arthritis, Addison’s disease, vitiligo, lupus, or type 1 diabetes) puts you at a higher risk⁶ of developing a second autoimmune disorder like Graves’ disease.
Deficiencies in key vitamins like vitamin D may⁷ contribute to the development of Grave's disease.
Smoking and stress⁸ are linked to the development of Grave's disease and acute hyperthyroidism.
Up to 8% of women get temporary hyperthyroidism⁹ after giving birth.
Hyperthyroidism can be difficult to diagnose. It's not uncommon for those with hyperthyroidism to go through various tests and treatments before arriving at their diagnosis, which is partially due to the variable nature of hyperthyroidism.
If your doctor suspects hyperthyroidism, they will often start with a physical exam. They will feel your neck for any enlargements, growths, or tenderness. In addition to a physical exam, your doctor may order blood tests or imaging to assist in the diagnosis.
There are a variety of blood tests used to diagnose and monitor hyperthyroidism. Remember, hyperthyroidism itself isn't a disease but is the cause of them. So, multiple types of blood tests may need to be completed to look for various issues:
High levels of circulating T4 or free T4 (fT4) are common complications of hyperthyroidism.
High levels of T3 can help indicate the severity of your hyperthyroidism. Often, T3 is used to track treatment progress, especially in certain forms of thyroid cancer.
Your pituitary gland uses thyroid-stimulating hormones (TSH) to regulate the levels of T3 and T4 in your blood. When levels of TSH are low, it can indicate an overactive thyroid.
Those with Graves’ disease often have high levels of thyroid antibodies (e.g., TPO, TG, TSI, etc.) and low levels of TSH.
Be aware that normal ranges of T3, T4, TSH, and thyroid antibodies vary depending on the test. Each laboratory uses its own reference ranges, so you should always discuss blood tests with your doctor directly.
Your doctor may also test your blood for vitamin deficiencies and other issues that may be related to hyperthyroidism.
Many people with an overactive thyroid experience physical changes (usually enlargement) to their thyroid. Doctors use a variety of imaging tests to help visualize your thyroid to assist in diagnosis. These include:
An ultrasound is the first (and most common) imaging test doctors typically utilize. You don't need to take any specific pills or liquids or make dietary changes before this test. You will lie down before a water-soluble gel is applied to your neck, which allows the doctor to move a probe across your neck to see your thyroid on a monitor.
In this type of scan, you swallow radioactive iodine a few hours before the procedure. Gamma rays pick up on iodine concentrations to detect abnormalities. Generally, nodules or tumors will absorb less iodine and appear darker on the scan.
If your physician suspects you may have a cancerous tumor on your thyroid, they may require a PET scan. You will likely be required to abstain from eating (12 hours) and drinking (~4 hours) before the scan.
A nurse or doctor will inject you with a radioactive tracer an hour before the procedure. Cancerous cells typically consume more tracer than healthy cells, making them appear brighter on the PET scan.
The treatment for hyperthyroidism varies depending on the underlying cause. Luckily, most causes of hyperthyroidism are easily treated, and many can be cured with modern treatments.
Common hyperthyroidism treatments include:
Medications like Methimazole and Propylthiouracil inhibit the synthesis of both T3 and T4, essentially reducing the number of hormones your thyroid can produce. These medications have side effects that you should discuss with your doctor or pharmacist.
Many people with Graves’ disease take beta-blockers to minimize their symptoms. Not only can beta-blockers reduce blood pressure and lower your heart rate, but they can also reduce symptoms of tremors and nervousness. Remember, discuss any side effects with your doctor.
Those with cancer or severe cases of Grave's disease can opt to surgically remove their thyroid. Depending on how much is removed, some people who get surgery will need to start treatment for hypothyroidism.
Fortunately, hypothyroidism is relatively easy to treat. After thyroid surgery, you may need to take thyroid hormone medication for the rest of your life.
While most people have entirely successful thyroid removal surgery, there are risks like laryngeal nerve injuries or bleeding.
Many people with Grave's disease do radioiodine treatment. During this treatment, you swallow radioiodine at a much higher dose than is used during a thyroid scan. This radioactive iodine collects in your thyroid and shrinks your glands.
Most people who get radioiodine therapy are cured of Grave's disease, but some aren't. Anywhere from 26.8 to 89.5%¹⁰ of people who get radioiodine treatment will need to be on thyroid replacement hormones, many for the rest of their lives.
Most people who have hyperthyroidism have a normal life expectancy. Symptoms can be managed with medication, and many will be cured through surgery or radioiodine treatment.
Make an appointment with your primary care physician if you have hyperthyroidism symptoms. If they think you may have hyperthyroidism, they will likely refer you to a thyroid specialist called an endocrinologist.
Some people with Graves’ disease may also need to see a dermatologist or ophthalmologist for skin or eye issues.
Remember, many of the symptoms of hyperthyroidism (e.g., tachycardia, tremors, etc.) can be signs of a more serious issue requiring immediate medical care.
Your thyroid is a small gland in your neck responsible for producing the hormones you need to survive.
Certain medical conditions or diseases can cause your thyroid to overproduce these hormones, causing symptoms such as nervousness, tachycardia, irritability, weakness, tremors, or even bulging eyes. These symptoms are also shared with many other diseases and conditions.
If you suspect you may have hyperthyroidism, consult your doctor. They may order blood tests, imaging tests or refer you to a specialist.
There are a variety of treatments for hyperthyroidism, including medications, beta-blockers, radioiodine, or surgery.
Postpartum thyroiditis | Johns Hopkins Medicine
Graves disease (2021)
Graves’ disease | (NIDDK) National Institute of Diabetes and Digestive and Kidney Diseases
Prevalence of grave’s disease varies widely by race/ethnicity | Endocrine Web
Multiple autoimmune syndrome (2010)
Postpartum thyroiditis | Johns Hopkins Medicine
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