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:

l Underactive thyroid (hypothyroidism)

l 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:

• Breathing

• Heart rate

• Digestion

• Energy production

• Muscle strength

• Body temperature

• Weight

• Mood

• Menstrual cycles

  
  

  Hypothyroidism

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

• Fatigue

• Weight gain

• Trouble tolerating cold

• Joint and muscle pain

• Dry skin and hair

• Temporary hair loss

• Heavy or irregular menstrual periods

• Fertility problems dealing with female reproduction

• Slowed heart rate

• Goiter (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 irritability

• Fatigue

• Muscle weakness

• Trouble tolerating heat

• Insomnia

• Tremor

• Rapid, irregular heart rate

• Frequent bowel movements and/or diarrhea

• Weight loss

• Mood swings

• Goiter

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 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 cancers

• Pregnancy

• Birth 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, perniciou  anemia, Sjögren’s syndrome, type 1 diabetes, rheumatoid arthritis, or lupus

Causes of hyperthyroidism include:

• Autoimmunity

• Excess iodine

• Thyroid nodules

• Thyroiditis

• Noncancerous 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

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.