What Is Hyperthyroidism?
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Medically reviewed by Kelly Wood, MD
Hyperthyroidism—often referred to as an overactive thyroid—is a condition that causes you to produce excess thyroid hormone. Your thyroid is a gland in your neck that controls body functions such as metabolism and temperature, among others. Having too much thyroid hormone can then cause symptoms that affect your mood, nervous system, digestion, heart, and skin.
Hyperthyroidism affects around 1.3% of people and is more common in people assigned female at birth. The condition is most often due to a problem with the thyroid gland itself, such as having a diagnosis for Graves' disease. If you have Graves' disease, are at risk for hyperthyroidism, or experience thyroid-related symptoms, it's a good idea to visit your healthcare provider to get tested.
Your provider can use lab testing and imaging tests to determine what's causing your symptoms. If you do receive a diagnosis for hyperthyroidism, your treatment plan will likely include medications—and in some cases, surgery.
Types of Hyperthyroidism
There are primary and secondary types of hyperthyroidism, which differ due to what's causing the excess production of thyroid hormone.
Primary Hyperthyroidism
In primary hyperthyroidism, a problem with the thyroid gland itself results in the overproduction of thyroid hormones. Laboratory tests will show too much triiodothyronine (T3) and thyroxine (T4)—two of the main hormones that your thyroid produces. Causes of primary hyperthyroidism include:
Graves' Disease
Toxic multinodular goiter
Toxic adenoma
Thyroid inflammation (thyroiditis)
Secondary Hyperthyroidism
In secondary hyperthyroidism, the thyroid gland itself is normal, but something is causing it to make too much thyroid hormone. This is usually due to an excess of thyroid hormone secretion from the brain. However, in some cases, cancers elsewhere in the body can produce hormones that look similar to thyroid hormone, causing an excess of T3 and T4. Secondary hyperthyroidism can occur as a result of:
Pituitary adenoma (brain tumor)
Choriocarcinoma (tumor in the uterus)
Testicular cancer
Related: Understanding TSH Levels
Symptoms
Because thyroid hormone plays such an important role in metabolic processes throughout the body, having too much causes a wide range of symptoms. Regardless of what's causing your hyperthyroidism, you can experience symptoms such as:
Fatigue
Hair loss
Feeling hot
Increased energy
Sweating more often
Irritability or anxiety
Softened nails
Blurry vision
Trouble concentrating
Unexplained weight loss
Hand tremors or shaking
Increased heart rate
Light or short menstrual periods
Muscle weakness
You can also have symptoms that are specific to Graves disease—an autoimmune condition that is the most common cause of hyperthyroidism:
Bulging eyes
Trouble seeing properly
Skin patches
Rash on your shins
Additionally, local symptoms due to the enlargement of the thyroid gland can occur. These may include:
Goiter, or bulging and swelling of the thyroid
Hoarse voice due to compression of the vocal cords
Difficulty swallowing
Trouble breathing
Causes
Hyperthyroidism occurs when you have too much thyroid hormone circulating in your blood. This can stimulate your metabolism and cause changes to your body temperature, weight, energy levels, and growth of skin, hair, and nails.
Why a change occurs in your thyroid hormone levels can depend on several factors including:
Inflammation of the thyroid (thyroiditis)
Autoimmune conditions such as Graves' disease
Damage to the thyroid from radiation
Hormonal changes during menstruation, pregnancy, postpartum, and menopause
Cancers and other conditions can produce hormones that are similar to the thyroid hormones
Risk Factors of Hyperthyroidism
You may be at an increased risk for developing hyperthyroidism if you:
Smoke cigarettes
Were assigned female at birth
Have a family history of thyroid disease
Eat a diet that is too high or too low in iodine
Use certain medications like Pacerone (amiodarone) or Lithoboid (lithium)
Diagnosis
If you suspect you have symptoms of a thyroid condition, it's essential to visit your provider for proper testing. During your appointment, your provider will likely ask about your medical history and conduct a physical exam to notice any prevalent symptoms of hyperthyroidism.
Depending on what your provider finds, they can also order additional testing such as blood tests and imaging scans that can help them make an accurate diagnosis, if needed. These tests include:
Blood tests: A blood test can look for your thyroid stimulating hormone (TSH), T3, and T4. Low levels of TSH can indicate that you have hyperthyroidism.
Imaging scans: While imaging tests can't officially diagnose you with a thyroid condition, they can help show changes to your thyroid gland and point to potential masses or nodules in your neck. Your provider can order scans such as an ultrasound or computed tomography (CT scans).
Related: How Is Thyroid Disease Diagnosed?
Treatment
The goal of treatment for hyperthyroidism is to bring your hormone level to a normal range and manage your symptoms. Your exact treatment plan will depend on what's causing your symptoms. In most cases of hyperthyroidism, beta-blockers like Tenormin (atenolol) can help manage symptoms initially.
Generally, the most common types of treatment include medication, radioiodine ablation, or surgery.
Medications
Antithyroid drugs, known as thionamides, that block and slow down the production of thyroid hormone can help normalize your thyroid hormone levels. Options for medication include:
Tapazole (methimazole)
PTU (propylthiouracil)
Keep in mind: these medications don't come without risks. In some cases, you might have side effects such as a low white blood cell count or liver toxicity and damage.
Radioactive Iodine Ablation
A more definitive treatment for primary hyperthyroidism is radioactive iodine ablation. With this treatment, a provider can give you a capsule or liquid form of radioactive iodine to ingest. When your thyroid absorbs the iodine, it slowly destruct the thyroid gland over a period of weeks to months. After this therapy, most people require thyroid hormone replacement medication since their thyroid gland is no longer able to make enough thyroid hormone.
It's important to note that people who are pregnant or breastfeeding should not undergo radioactive iodine ablation due to the risks of radiation.
Surgery
Surgery to remove the thyroid gland is not usually the first option for treatment. However, this can be a good option if other treatments have not been working for you. Your provider can recommend surgery if medication and a radioactive iodine ablation do not improve your symptoms or stabilize your thyroid hormone levels. If you prefer to have surgery instead of trying other treatments, talk to your provider about how to move forward.
It's important to note that surgery does come with its own set of risks such as infection, bleeding, and damage to surrounding tissue. If you do get surgery to remove your thyroid gland, similar to an ablation, you will often be required to take thyroid hormone supplements.
How to Prevent Hyperthyroidism
There's no surefire way to reduce your risk of hyperthyroidism. However, there are some things you can try to keep your hormone levels in a normal range. These include:
Quitting smoking
Getting an appropriate amount of iodine in your diet
While screening for thyroid disorders is not recommended in people without symptoms, if you notice any symptoms of hyperthyroidism or have a family history of the condition, it's a good idea to see a healthcare provider who can order a blood test to check your thyroid levels.
Related Conditions
When hyperthyroidism is due to an autoimmune disease like Graves' disease, you might be at an increased risk of also developing one of the following conditions, including:
Systemic sclerosis
Pernicious anemia
In some cases, you can have a condition that can co-occur with hyperthyroidism, such as:
Ovarian cancer
Testicular cancer
Heart disease or arrhythmias
Osteoporosis
Infertility
Living with Hyperthyroidism
While symptoms of hyperthyroidism can be frustrating and affect your daily life, the good news is that hyperthyroidism is treatable. While lifelong therapy may be required, you should generally be able to live a long and healthy life.
Depending on the type of treatment you and your healthcare provider choose, you may need to take thyroid hormone supplementation to help your body produce thyroid hormone that regulates your metabolism and other vital body functions. Keep in mind: it's a good idea to stay in touch with your healthcare provider as it's important to have regular blood tests to ensure that your thyroid levels are in an appropriate range.
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