More than 12% of people in the United States will develop thyroid disease at some point in their lifetime. Millions of Americans are already living with it, and many may not even know it.

The two main types of thyroid conditions are:

  • Underactive thyroid (hypothyroidism)Overactive thyroid (hyperthyroidism)

This article reviews facts and statistics to help you understand thyroid disease and its impact.

Thyroid Disease Overview

The thyroid is a butterfly-shaped gland in the front of your throat. Through the production and release of thyroid hormones, it regulates many automatic processes in your body. These include:

  • BreathingHeart rateDigestionEnergy productionMuscle strengthBody temperatureWeightMoodMenstrual cycles

Hypothyroidism

In hypothyroidism, your thyroid gland doesn’t make enough thyroid hormone. This slows down your metabolism and causes:

  • FatigueWeight gainTrouble tolerating coldJoint and muscle painDry skin and hairTemporary hair lossHeavy or irregular menstrual periodsFertility problems dealing with female reproductionSlowed heart rateGoiter (an enlarged thyroid that feels like a lump in your throat)

Some cases of hypothyroidism are caused by an autoimmune condition called Hashimoto’s disease. 

Hyperthyroidism

In hyperthyroidism, your thyroid produces too much thyroid hormone. This speeds up many of your body’s processes. Symptoms include:

  • Nervousness or irritabilityFatigueMuscle weaknessTrouble tolerating heatInsomniaTremorRapid, irregular heart rateFrequent bowel movements and/or diarrheaWeight lossMood swingsGoiter

Some cases of hyperthyroidism are caused by an autoimmune disorder called Graves’ disease. It can also be caused by thyroiditis (inflamed thyroid gland), growths called thyroid nodules, and too much iodine in the blood. Thyroid hormone production relies on iodine.

How Common Is Thyroid Disease?

Thyroid disease is fairly common. An estimated 20 million people in the United States have thyroid disease. As many as 60% of people with thyroid disease are not aware that they have it.

Hypothyroidism is about 7.5 times more common than hyperthyroidism. In addition, experts estimate that thyroid disease is becoming more common. However, it’s difficult to determine if rising rates are due to more cases, a better means of diagnosing thyroid disease, or both.

Thyroid Disease by Ethnicity

The rates of autoimmune thyroid diseases are different among ethnic groups. 

Hashimoto’s disease appears to be more common in White Americans and less common in Black Americans, Asian Americans, and Pacific Islanders.

Graves’ disease appears to be more common in Americans who are Black and Pacific Islander. It is less common in people who are White.

Thyroid Disease by Age and Sex

Rates of thyroid disease vary based on age and sex.

Thyroid disease becomes more common as people age. Hypothyroidism is most often diagnosed between the ages of 30 and 50. Hyperthyroidism diagnoses are most common between ages 20 and 40.

Thyroid disease is significantly more common in women. Hypothyroidism is believed to be about 9times more common in people assigned female at birth. Hyperthyroidism is believed to be between 2 and 10 times more likely in females. It’s estimated that about 1 in every eight women will develop thyroid problems, compared to 1 in 17 for the total population.

Why being female makes you more prone to thyroid disease isn’t fully understood. Estrogen, considered the primary female hormone, is thought to play a role.

Also, women are thought to be genetically more susceptible to autoimmune disease than people assigned male at birth. This may be due to a stronger immune response in females.

Causes of Thyroid Disease and Risk Factors

Causes of hypothyroidism include:

  • Autoimmunity (most common in the United States)Iodine deficiency (rare in the United States but quite common worldwide)Radiation therapy for head and neck cancersPregnancyBirth defect in the thyroid gland

Hypothyroidism can also be caused by treatments for hyperthyroidism, including radioactive iodine treatments and surgical removal of part of all of the thyroid gland.

Risk factors for hypothyroidism include:

  • A history of thyroid problems such as goiter
  • Previous thyroid surgery
  • A family history of hypothyroidism
  • Recent pregnancy or childbirth
  • Use of nicotine products, such as cigarettes or vaping
  • Having Turner syndrome, pernicious anemia, Sjögren’s syndrome, type 1 diabetes, rheumatoid arthritis, or lupus

Causes of hyperthyroidism include: 

  • AutoimmunityExcess iodineThyroid nodulesThyroiditisNoncancerous tumors on the pituitary gland, which is involved in thyroid function

Temporary hyperthyroidism can be caused by overmedication with thyroid replacement hormone.

Risk factors for hyperthyroidism include:

  • Family history of thyroid disease
  • Having pernicious anemia, type 1 or 2 diabetes, or primary adrenal insufficiency (Addison’s disease)
  • Eating a lot of high-iodine foods or taking iodine-containing medication
  • Use of nicotine products, such as cigarettes or vaping
  • Recent pregnancy or childbirth

What Are the Mortality Rates for Thyroid Disease?

Thyroid diseases aren’t typically fatal. Also, mortality rates have dropped as diagnosis and treatments have improved.

In a 2021 study, people being treated for hypothyroidism had a slightly higher mortality rate than study participants who did not have hypothyroidism.

Untreated hypothyroidism can lead to potentially fatal heart problems and a life-threatening complication called myxedema, which is extreme hypothyroidism. However, myxedema is rare because most people get treatment before hypothyroidism becomes this advanced.

A study of mortality in people treated for hyperthyroidism noted deaths at follow-up (up to 17 years later) of 28.7%. The rate in people who weren’t treated was 34.2%.

Untreated hyperthyroidism can lead to heart problems that may cause:

  • Blood clots
  • Stroke
  • Heart failure
  • Other cardiac problems

All of those have the potential to be fatal.

An overactive thyroid plus major stress on your body (such as a heart attack or severe injury) can lead to a life-threatening condition called a thyroid storm. It’s a medical emergency that requires hospitalization.

Screening and Early Detection

The American Thyroid Association recommends routine thyroid screening at age 35, with tests performed every 5 years.

Symptoms of Thyroid Storm

  • Agitation or restlessnessLoss of consciousnessConfusionDiarrheaIncreased body temperatureRacing or pounding heartShakingSweatingBulging eyeballs

However, the U.S. Preventive Services Task Force (USPSTF) doesn’t recommend screening in nonpregnant adults without symptoms of thyroid disease.

Early diagnosis and treatment may help prevent dangerous complications of thyroid disease. If you’re concerned about your thyroid function, ask your healthcare provider about getting the tests.

Summary

Your thyroid gland controls many important bodily functions. Too little thyroid hormone (hypothyroidism) slows down these processes while too much (hyperthyroidism) speeds them up.

Thyroid disease is common, especially in people assigned female at birth. Rates of different thyroid disorders vary by age, sex, and ethnicity. Causes include autoimmunity, genetics, and other factors.

Thyroid disease is rarely fatal, but if left untreated, it can lead to life-threatening complications such as myxedema and thyroid storm.