What Is Hyperthyroidism?

In This Article
Table of Contents

Hyperthyroidism, sometimes referred to as an overactive thyroid, is a disease that occurs when your thyroid gland—a small, butterfly-shaped gland located in your neck—produces too much thyroid hormone. Generally, the thyroid gland receives a hormone called thyroid-stimulating hormone (TSH) from the pituitary gland in your brain, which is stimulated by a part of the brain called the hypothalamus.

The thyroid uses the TSH to regulate how much thyroid hormone—specifically, T3 and T4—it makes. With an overactive thyroid, too much T3 and T4 are produced.

Hyperthyroidism can increase metabolism, leading to weight loss, thinning hair, sweating, and more. Blood tests diagnose it, and treatment typically involves prescription medication, though serious cases may warrant ablation or surgical removal of the thyroid gland.

By gaining some sense of what it feels like to have hyperthyroidism, as well as how this disease is identified and treated, you can hopefully feel empowered as you navigate through your own thyroid journey—from diagnosis to management. 

Hyperthyroidism Symptoms

When functioning normally, your thyroid uses dietary iodine to produce thyroid hormone. This hormone regulates how your organs, glands, tissues, and cells use oxygen and energy. With excess production, processes in your body "speed up." So, for example, your heart pumps blood faster (causing a racing heart), and your brain goes into overdrive, making it difficult to sleep.

Other Symptoms of Hyperthyroidism

  • Anxiety and/or irritability
  • Weight loss without dieting
  • Feeling hot when others are cold (heat intolerance)
  • Sweating more than usual
  • Thinning hair and unusually smooth skin
  • Muscle weakness
  • A visible or palpable lump in the area of your thyroid/neck (goiter)

These symptoms, however, are just the tip of the iceberg. There are many more symptoms, some more subtle than others, that can point to a diagnosis of hyperthyroidism.


There are a number of health conditions or situations that cause hyperthyroidism.

Graves’ disease is the most common cause, affecting over 70 percent of people with hyperthyroidism. In Graves' disease, your immune system inappropriately produces antibodies, known as thyroid stimulating antibodies (TSI), that overstimulate your thyroid gland, causing it to overproduce thyroid hormone.

Other causes of hyperthyroidism include:

  • Toxic multinodular goiter
  • Hyperfunctioning thyroid nodule (called toxic adenoma) 
  • Thyroiditis, an inflammatory condition that may be triggered by factors like infection, trauma, radiation, or the postpartum period.
  • Taking too much thyroid hormone, either by prescription or supplement use
  • Iodine-excess hyperthyroidism
  • Temporary hyperthyroidism in Hashimoto's disease
  • Transient hyperthyroidism of hyperemesis gravidarum
  • Pituitary-induced hyperthyroidism
  • Fetal-neonatal hyperthyroidism


Diagnosis of hyperthyroidism involves several key steps:

Clinical Examination

During a clinical examination, your doctor will evaluate your personal and family history of thyroid and autoimmune disease, review your symptoms, and examine your thyroid manually. The doctor will also look for other clinical signs of hyperthyroidism like a high heart rate, a goiter, and exaggerated reflexes, among others.

hyperthyroidism diagnosis
© Verywell, 2018 

Blood Testing

Blood tests are used to diagnose hyperthyroidism. The primary blood test used is the thyroid-stimulating hormone (TSH) blood test.

When your thyroid is producing too much thyroid hormone, the TSH level is low.

Your doctor may also order a free thyroxine (FT4) or free thyroxine index (FTI), depending on your medical history and the results of your TSH blood test. People with hyperthyroidism will have a high FT4 or FTI.

Other blood tests your doctor may order include:

  • Triiodothyronine (T3)
  • Thyroid antibodies

Imaging Test

A thyroid scan called the radioactive iodine uptake scan (RAI-U) is used to determine the cause of your hyperthyroidism (for example, Graves' disease versus toxic multinodular goiter).


Hyperthyroidism is treated using three different approaches:

  • Drug treatment with antithyroid drugs
  • Ablation of the thyroid gland with radioactive iodine, known as RAI
  • Surgery to remove all or part of the thyroid

Which treatment you undergo depends on a number of factors, such as the cause and severity of your hyperthyroidism, your age, your preference, and your overall health.

You may also be prescribed a type of medication called a beta-blocker to slow down your heart rate and ease your tremor or anxiety.

Not treating most forms of hyperthyroid can lead to an irregular heartbeat, high blood pressure, and even a risk of heart attack or stroke, as part of a life-threatening complication called a thyroid storm.

In some cases, treated patients will go into remission due to antithyroid drugs or immune system changes. However, the majority of Graves' and hyperthyroidism patients do require lifelong antithyroid drug treatment or one of the permanent procedures listed above.

A Word From Verywell

Knowledge is power. By learning the basics of hyperthyroidism, you are already a step farther on your (or your loved one's) thyroid journey.

While a diagnosis of hyperthyroidism may seem overwhelming at times (it's normal to be nervous about taking a new medication or undergoing a new procedure or surgery), hopefully your mind is at ease knowing that this disease is treatable.

Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Hyperthyroidism. American Thyroid Association.

  2. Bland RD, Clarke TL, Harden LB. Rapid infusion of sodium bicarbonate and albumin into high-risk premature infants soon after birth: a controlled, prospective trial. Am J Obstet Gynecol. 1976;124(3):263-7. doi:10.1155/2013/813264

  3. Caturegli P, De remigis A, Rose NR. Hashimoto thyroiditis: clinical and diagnostic criteria. Autoimmun Rev. 2014;13(4-5):391-7. doi:10.1016/j.autrev.2014.01.007

  4. De leo S, Lee SY, Braverman LE. Hyperthyroidism. Lancet. 2016;388(10047):906-918. doi:10.1016/S0140-6736(16)00278-6

  5. Kravets I. Hyperthyroidism: Diagnosis and Treatment. Am Fam Physician. 2016;93(5):363-70.

Additional Reading