23 possible symptoms of an overactive thyroid

Medically reviewed by Rosanna Sutherby, PharmD on October 13, 2020. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

If you’ve been experiencing symptoms like nervousness, fatigue, or heat sensitivity—to name just a few examples—you might be wondering if it could have something to do with your thyroid function. These and other symptoms are all possible consequences of an overactive thyroid gland. So if you’re interested in learning more about common overactive thyroid symptoms, you’ve come to the right place. Read on to discover what the thyroid does in the body, signs and symptoms of an overactive thyroid gland (plus possible causes), how the condition is diagnosed, thyroid testing, and more.

Check if your thyroid hormones are balanced from the convenience of home with the Everlywell at-home Thyroid Test.


What is the thyroid?

The thyroid is a small gland located right below the larynx (the voice box) at the base of the neck. Because it’s involved in many body processes and functions (such as metabolism) through the controlled release of hormones, this butterfly-shaped gland plays a key role in one’s overall health.

What does the thyroid do?

The thyroid produces two main hormones—thyroxine (T4) and triiodothyronine (T3)—which circulate throughout the bloodstream, acting as “chemical messengers” that help regulate a wide variety of processes in the body. For instance, metabolism, body temperature, and heart rate are all influenced by thyroid hormones.

Because the thyroid is a crucial part of the body, when it malfunctions—becoming overactive (hyperthyroidism) or underactive (hypothyroidism)—your health can suffer and you may experience a variety of symptoms. If the thyroid gland is overactive, it produces an excessive amount of thyroid hormones—disturbing the thyroid’s regulatory function, which relies on balanced thyroid hormone levels. On the flip side, if the thyroid is underactive, that means it’s not making enough hormones.

In this article, we’ll focus on symptoms associated with an overactive thyroid. (Related: Hypothyroidism vs. hyperthyroidism: the key differences explained)

Signs and symptoms of an overactive thyroid

From weight loss to nervousness or anxiety, there are many different overactive thyroid symptoms someone can potentially experience. So, without further ado, here are 23 common signs and symptoms to consider if you suspect your thyroid gland has shifted into overdrive. List of overactive thyroid symptoms to be aware of.

  1. Nervousness and anxiety
  2. Difficulty sleeping
  3. Mood swings
  4. Enlarged thyroid gland (leading to swelling in your neck)
  5. Fatigue
  6. Sensitivity to heat
  7. Fast or irregular heartbeat
  8. Twitching or trembling
  9. Weight loss
  10. Muscle weakness
  11. Persistent thirst and/or increased appetite
  12. Loose nails
  13. Hair loss or thinning
  14. Eye problems (dryness, redness, or vision problems)
  15. Diarrhea
  16. Itchiness
  17. Raised rash (hives)
  18. Hyperactivity (which may make it hard to stay still)
  19. Lack of interest in sex
  20. Unusually warm skin
  21. Excessive sweating
  22. Menstrual cycle irregularities (including short or light periods)
  23. Changes in bowel movement patterns

Note: Keep in mind that these signs and symptoms can occur for reasons other than an overactive thyroid—so if you’re experiencing any of the above, discussing it with your healthcare provider is one of the best next steps to take.

Reasons for an overactive thyroid

Now that you’re more familiar with overactive thyroid symptoms, you may be wondering what causes a thyroid problem like this in the first place. Here are several possible reasons for an overactive thyroid.

Graves’ disease

Graves’ disease is the most common cause of hyperthyroidism (another term for overactive thyroid) in the United States. It’s estimated that approximately 3 in 4 people with an overactive thyroid have Graves’ disease—an autoimmune condition that involves one’s own immune system attacking the thyroid gland, causing it to become overactive.

The precise cause of this autoimmune disease is not yet known; however, what we do know is that it commonly runs in families. It’s also known that, in some cases, Graves’ disease can affect other parts of the body—not just the thyroid gland—such as skin and eyes. Graves’ eye disease (also known as Graves' ophthalmopathy or Graves' orbitopathy) may occur in 25-50% of people diagnosed with Graves’ disease, according to some estimates. Symptoms of Graves’ eye disease can include:

  • A feeling of irritation or grittiness in the eyes
  • Redness or inflammation of the white part of the eyeball
  • Excessive tearing
  • Dry eyes
  • Swelling of the eyelids
  • Sensitivity to light
  • Bulging of the eyes (called proptosis)
  • Double vision

Excessive iodine intake

High iodine intake can lead to excess thyroid hormone production. This can occur due to high dietary consumption of iodine (by eating foods rich in iodine, such as kelp). This can also come as a result of taking medication that contains iodine (such as certain medications that are prescribed to help control an irregular heartbeat).

Note: Be sure to always consult with your healthcare provider first before making any changes to your medication regimen.

Pituitary adenoma

Pituitary adenomas are benign tumors that affect the pituitary gland. The pituitary gland is located at the base of the brain and secretes hormones that influence thyroid hormone production levels.

Thyroid cancer

In rare cases, a cancerous tumor in the thyroid affects the body’s production of thyroid hormones.

Hyperfunctioning thyroid nodules

Also known as toxic adenoma, toxic multinodular goiter, or Plummer's disease, this type of hyperthyroidism happens when a benign tumor in the thyroid produces too much T4. The thyroid may also become enlarged.

Thyroid nodules

If lumps, or nodules, develop on the thyroid, this can lead to hyperthyroidism. These nodules are often non-cancerous, but the thyroid tissue they contain can cause the body to produce more thyroid hormones than necessary.


Thyroiditis refers to inflammation of the thyroid (this sometimes occurs shortly after pregnancy, for example), which may result in the overproduction of thyroid hormones.

Risk factors for an overactive thyroid

  • A family history of Graves' disease or autoimmune disorders
  • Women are more likely to develop hyperthyroidism compared to men (studies show that hyperthyroidism occurs in about 10x more women than men)
  • A personal medical history of specific chronic illnesses, including type 1 diabetes, pernicious anemia, or primary adrenal insufficiency
  • Common viral infections
  • Pregnancy (a small percentage of women develop postpartum thyroiditis, or an overactive thyroid after pregnancy)
  • Age (hyperthyroidism is more common in people over the age of 60)
  • Excess iodine intake

How an overactive thyroid is diagnosed

An overactive thyroid is typically diagnosed by a healthcare provider based on an evaluation of factors such as symptoms, medical history, and results from a blood test (known as a thyroid function test).

Thyroid function test

This test uses a blood sample to measure the levels of the following hormones:

  • Thyroid-stimulating hormone (TSH) – the hormone produced by the pituitary gland that helps control the thyroid’s hormone production
  • Triiodothyronine (T3) and thyroxine (T4) – hormones produced by the thyroid gland to help regulate various functions in the body

Low TSH levels and high levels of T3 and/or T4 may indicate an overactive thyroid.

Other tests

A healthcare provider may also recommend a blood test that checks for thyroid antibodies. Thyroid antibodies are commonly found in individuals who have Graves' disease.

An additional blood test called erythrocyte sedimentation rate (ESR) may also be conducted to look for inflammation in the body. Inflammation of the thyroid gland may lead to thyroiditis, as mentioned above. Additionally, a thyroid scan—also called nuclear medicine thyroid imaging—might be done to look for thyroid nodules.

Everlywell Thyroid Test

Our Thyroid Test lets you easily check your thyroid hormone levels from the convenience of home, plus a type of thyroid antibody known as TPOab (thyroid peroxidase antibody).

What it measures:

Thyroid-stimulating hormone (TSH)

TSH is the hormone responsible for controlling hormone production by the thyroid gland. It’s considered one of the most sensitive markers for screening for thyroid conditions.

Free T3 and free T4

Our test measures these key thyroid hormones so you can see whether your levels are low, normal, or high when compared to the reference range.

Thyroid peroxidase antibodies (TPOab)

TPOab can bind to certain thyroid enzymes, thereby suppressing thyroid function. TPOab levels are often elevated in Hashimoto's disease, the most common type of hypothyroidism (underactive thyroid) in the United States.

Treatment for an overactive thyroid

If you experience overactive thyroid symptoms and are diagnosed with hyperthyroidism, it can help to know that effective treatments do exist (and should be discussed with your healthcare provider). Possible treatments include the following.

Thyroid medication

Thionamides keep your thyroid from producing excess hormones and are often used as a treatment for an overactive thyroid. The main types are carbimazole and propylthiouracil. A beta-blocker may also be given to help relieve your symptoms.

Some people may need to take medicine for years (or throughout their entire life), though others may be able to stop eventually once their thyroid hormone levels are under control.

Radioactive iodine treatment

Radioactive iodine treatment is a type of radiotherapy that kills cells in the thyroid gland to curb hormone production. Some people need only one treatment.

Thyroid surgery

If you suffer from severe eye problems because of your thyroid, your thyroid is swollen, or your overactive thyroid symptoms keep coming back, a healthcare provider may recommend a surgical procedure to remove some or all of your thyroid.

Check your thyroid hormone levels from the convenience of home with the Everlywell Thyroid Test.


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