Hyperthyroidism occurs when your thyroid gland is overproducing thyroid hormones. This can cause symptoms that may include weight loss and increased appetite.

Several health conditions can lead to hyperthyroidism, most commonly Graves’ disease.

The thyroid is a small, butterfly-shaped gland located at the front of your neck. It produces thyroxine (T4) and triiodothyronine (T3), which are two primary hormones that control how your cells use energy. Your thyroid gland regulates your metabolism through the release of these hormones.

When your thyroid makes too much T3, T4, or both, it speeds up your body’s systems, causing distress. Timely diagnosis and treatment of hyperthyroidism can relieve symptoms and prevent complications.

Some symptoms of hyperthyroidism may be physically obvious, while others are subtle, and may be hard to notice at first. Sometimes hyperthyroidism is mistaken for anxiety.

According to the National Institutes of Health (NIH), hallmark signs and symptoms of hyperthyroidism include:

  • weight loss, but with an increased appetite
  • rapid or irregular heartbeat
  • feeling nervous or irritable
  • feeling fatigued, but having trouble sleeping
  • hand tremors, muscle weakness
  • getting easily overheated
  • frequent bowel movements

The thyroid gland itself can swell into a goiter, which can be either symmetrical or one-sided. A goiter is an enlargement of the gland, and it’s often visible as a bulge or puffiness at the base of your neck. The most common cause of a goiter is iodine deficiency.

You may also experience prominent or bulging eyes. This is medically known as exophthalmos, and it’s associated with Graves’ disease.

Longterm and untreated thyroid disease can also cause brittle hair, and hair loss.

Untreated, hyperthyroidism can contribute to an increased risk of:

  • Thyroid storm: A thyroid storm is a rare health condition that occurs as a result of untreated hyperthyroidism. Your body enters overdrive as a result of too many thyroid hormones in its system. A thyroid storm is a potentially life threatening combination of symptoms, including rapid heart rate, high blood pressure, and fever.
  • Pregnancy complications: This includes people with existing thyroid disorders and people who develop hyperthyroidism during pregnancy. High thyroid hormone levels can harm both pregnant people and the fetus. Risks include miscarriage and premature birth. Testing thyroid hormone levels during pregnancy can detect hyperthyroidism. The doctor will determine the need for treatment based on the levels.
  • Osteoporosis: Hyperthyroidism can cause your bones to become weak and thin, which can lead to osteoporosis. Taking vitamin D and calcium supplements during and after treatment can help improve bone health. Getting adequate exercise or daily physical activity in addition to hyperthyroidism treatment also helps prevent osteoporosis.
  • Cancer: Some types of cancer can present with hyperthyroidism. A 2018 research overview reported that thyroid cancer in hyperthyroid patients was more “aggressive” and had a worse outlook than in euthyroid patients (those with a healthy thyroid).

A variety of conditions can cause hyperthyroidism. Graves’ disease, an autoimmune disorder, is the most common cause of hyperthyroidism. In Graves’ disease, your immune system attacks your thyroid gland with antibodies, resulting in the release of too much hormone.

Tell your doctor if any relatives have been diagnosed with hyperthyroidism, so they can get an accurate picture of your risk factors.

Aside from Graves’ disease, other causes of hyperthyroidism include:

  • excess iodine
  • thyroiditis (inflammation of the thyroid)
  • toxic thyroid nodules (toxic adenoma)
  • tumors of the ovaries or testes

Thyrotoxicosis and hyperthyroidism don’t mean the same thing, even though they’re sometimes used interchangeably. Hyperthyroidism (and its many forms) are actually all under the umbrella of thyrotoxicosis.

Hyperthyroidism refers to your thyroid’s physical overproduction of hormones. Thyrotoxicosis refers more broadly to the presence of too much thyroid hormone in your body, regardless of whether it came from the gland, medication, or other cause.

In evaluating you for hyperthyroidism, a doctor will collect your personal and family medical history, and conduct a physical exam. Doctors usually diagnose hyperthyroidism based on symptoms, clinical signs, and lab tests.

These diagnostic tests include:

While primary care doctors can order some of these tests, it’s best to see an endocrinologist. Endocrinologists specialize in treating and managing hormone-related health conditions.

  • Medication: Anti-thyroid medications prevent the thyroid from making hormones. The most common anti-thyroid medications are a class called thionamides, which includes the drugs methimazole (MMI) and propylthiouracil (PTU).
  • Radioactive iodine: Radioactive iodine (RAI), also just called radioiodine, effectively destroys the cells that produce thyroid hormones without damaging other bodily tissues. It is usually taken as an oral tablet or liquid. Most people who receive radioiodine treatment for hyperthyroidism develop the opposite condition, hypothyroidism. However, this is easier to treat, and you’ll take a daily thyroid hormone supplement. RAI is also used in higher doses to treat thyroid cancer.
  • Surgery: During a thyroidectomy, all or part of your thyroid gland is removed. This surgery may be recommended for certain people with hyperthyroidism, but it’s evaluated on an individual basis.

FDA recall alert

Certain brands and strengths of medication for hypothyroidism (underactive thyroid) have been recalled. This is due to the medication having a less active drug (levothyroxine) than they are supposed to.

You can search all FDA recalls and safety alerts here.

Taking recalled tablets can lead to symptoms of hypothyroidism, such as fatigue, constipation, hair loss, and depression. Reduced effectiveness can be particularly dangerous for older people and those who are pregnant.

Call your pharmacist to find out if your medication has been recalled. Don’t stop taking the medication unless advised to do so by your healthcare professional.

To summarize, the main risk factors for hyperthyroidism are:

  • Sex: Females are much more likely to have hyperthyroidism than males. Experts believe this may have to do with hormones.
  • Pregnancy: Pregnancy can stimulate hyperthyroidism in some people, which can cause complications for both parent and fetus.
  • Age: You’re considered at higher risk for hyperthyroidism as an older adult, especially after age 60.
  • Genetics: A family history of hyperthyroidism usually indicates an increased likelihood of developing the condition.
  • Iodine exposure: You may get too much iodine from certain medications or foods.
  • Having another health condition: People with type 1 diabetes, primary adrenal insufficiency, or pernicious anemia are considered more at risk.

There are many reasons your thyroid might start overproducing thyroid hormones.

A genetic predisposition to thyroid conditions like Graves’ disease, having too much iodine in your system, or being pregnant can all contribute to hyperthyroidism. Eating well, exercising, and avoiding smoking can all help reduce your risk.

Hyperthyroidism is diagnosed based on symptoms, blood tests, and imaging. It is treated primarily with medication, radioiodine therapy, and if necessary, surgery to remove all or part of the thyroid gland.

Talk with your doctor if you believe you’re experiencing thyroid-related health concerns. You may be referred to an endocrinologist, who will evaluate you, and conduct the necessary tests.