Thyroid disease is one of the most common hormone conditions in the United States, and it affects women far more often than men. An estimated 20 million Americans have some form of thyroid disease, and the American Thyroid Association (ATA) reports that up to 60% do not know they have it. The two broad problems are an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism), and the underactive form is by far the more common. Below, every figure is tied to a primary source and its data year.
Overview: thyroid disease at a glance
The thyroid is a small, butterfly-shaped gland in the neck that sets the body's metabolic pace. When it makes too little hormone (hypothyroidism) or too much (hyperthyroidism), it can affect energy, weight, heart rate, mood, periods, and bone health. According to the ATA, more than 12% of the U.S. population will develop a thyroid condition at some point in life, and 1 in 8 women will develop a thyroid disorder. Because early symptoms are vague, many cases go undetected for years — see our guide to at-home thyroid tests and what a TSH result means.
How common is thyroid disease?
National survey data give the clearest population estimates:
- Hypothyroidism: Nearly 5 in 100 Americans ages 12 and older have an underactive thyroid, though "most cases are mild," per the NIDDK's 2021 review.
- Hyperthyroidism: About 1 in 100 Americans ages 12 and older have an overactive thyroid (NIDDK, 2021 review).
- Earlier benchmark: In NHANES III (survey years 1988–1994, published 2002), hypothyroidism was found in 4.6% of the population (0.3% overt, 4.3% subclinical) and hyperthyroidism in 1.3% (0.5% overt, 0.7% subclinical).
The gap between diagnosed cases and laboratory evidence is why the ATA highlights the 60% undiagnosed figure: a large share of people have abnormal thyroid labs without a formal diagnosis.
| Measure | Figure | Source (data year) |
|---|---|---|
| Americans with some thyroid disease | ~20 million | American Thyroid Association |
| Will develop a thyroid condition in their lifetime | >12% | American Thyroid Association |
| Undiagnosed / unaware | Up to 60% | American Thyroid Association |
| Women's lifetime risk | 1 in 8 | American Thyroid Association |
| Women vs. men | 5–8x more likely | American Thyroid Association |
| Hypothyroidism (ages 12+) | ~5 in 100 (5%) | NIDDK (2021) |
| Hyperthyroidism (ages 12+) | ~1 in 100 (1%) | NIDDK (2021) |
| Hypothyroidism | 4.6% | NHANES III (1988–1994) |
| Hyperthyroidism | 1.3% | NHANES III (1988–1994) |
| Hashimoto's more common in women | 4–10x | NIDDK (2021) |
| Graves' share of hyperthyroidism | ~80% (4 of 5) | NIDDK (2021) |
Who thyroid disease affects
Sex
Women are consistently more affected. The ATA reports women are 5 to 8 times more likely than men to have thyroid problems. Autoimmune disease drives much of that gap: Hashimoto's disease is 4 to 10 times more common in women than men (NIDDK, 2021). Because this overlaps with the menopause transition, thyroid symptoms are easy to miss — fatigue and unexplained weight gain, for instance, are common to both — so it is worth comparing notes in our menopause hub.
Age
Risk rises with age. The NIDDK (2021) notes that hypothyroidism is more common in people older than 60, and hyperthyroidism is also more common with age. Hashimoto's disease "more often develops in women ages 30 to 50" (NIDDK, 2021).
Race and ethnicity
Where solid U.S. data exist, autoimmune thyroid markers vary by group. In NHANES III (1988–1994), thyroid peroxidase antibodies were less common in Black Americans (4.5%) than in white Americans (12.3%), tracking with lower measured rates of thyroid dysfunction in Black adults.
Hashimoto's and Graves': the leading causes
Hashimoto's disease is the most common cause of hypothyroidism (NIDDK, 2021). On the overactive side, Graves' disease is the leading cause of hyperthyroidism: about 4 out of 5 (roughly 80%) hyperthyroidism cases in the U.S. are Graves', and Graves' affects nearly 1 in 100 Americans (NIDDK, 2021). Both are autoimmune, and both hit women hardest.
Related risks
Untreated thyroid disease can affect the whole body. Because thyroid hormone influences heart rate, cholesterol, bone turnover, and metabolism, thyroid problems are linked to changes in heart health, bone health, and weight and metabolism. Thyroid symptoms also overlap heavily with perimenopause, so testing is often worthwhile when symptoms are unclear.
Trends
Long-run U.S. prevalence has stayed broadly in the same range across surveys — roughly 1% for hyperthyroidism and about 5% for hypothyroidism. The biggest "hidden" burden is undiagnosed and subclinical cases rather than a dramatic rise in disease. Because so many cases are mild or silent, measured prevalence depends heavily on how widely people are screened, which is part of why estimates vary between sources.
FAQ
How common is thyroid disease overall?
An estimated 20 million Americans have some form of thyroid disease (ATA). By type, nearly 5 in 100 U.S. adults have hypothyroidism and about 1 in 100 have hyperthyroidism (NIDDK, 2021).
Why are women affected so much more often?
Women are 5 to 8 times more likely than men to have thyroid problems (ATA), largely because autoimmune thyroid disease — the main cause — is far more common in women. Hashimoto's is 4 to 10 times more common in women (NIDDK, 2021).
How many cases go undiagnosed?
The ATA estimates up to 60% of people with thyroid disease are unaware of their condition, which is why a simple TSH blood test is often recommended when symptoms are unclear.
The bottom line: Thyroid symptoms are easy to confuse with stress, aging, or menopause. If you have ongoing fatigue, weight changes, or a racing heart, talk to your clinician about a simple TSH blood test — this article is for education, not diagnosis.
