Thyroid Disorders in the United States: Symptoms, Causes & Treatment Options
Updated: Sep 8
Written by Dr. Zack Ferris in TheSkyMeds Editorial Standards
Medically reviewed by Jonathan Reed, Medical Content Reviewer Feb 23 2026
Thyroid disorders in the United States affect how the body produces or responds to thyroid hormones, which help regulate energy use, heart rate, temperature, digestion, and many other functions. Two of the best-known conditions are hypothyroidism, in which the thyroid does not make enough hormone, and hyperthyroidism, in which thyroid activity is too high. Other thyroid problems include Hashimoto’s disease, Graves’ disease, thyroiditis, goiter, thyroid nodules, and thyroid cancer. Symptoms can range from fatigue, weight changes, and temperature sensitivity to heart-rate changes, neck swelling, or menstrual problems, but symptoms alone cannot confirm a thyroid disorder. Diagnosis usually involves medical history, an examination, thyroid blood tests, and sometimes imaging or other testing. Treatment depends on the specific disorder and may include thyroid hormone replacement, antithyroid medicines, radioactive iodine, surgery, monitoring, or condition-specific cancer treatment. This guide explains the main symptoms, causes, diagnosis, and treatment options US adults should understand.
What Are the Most Common Types of Thyroid Disorders?
Thyroid disorders are a group of conditions rather than one disease. Some change the amount of thyroid hormone in the body, while others primarily affect the thyroid gland’s size or structure.
The thyroid is a small, butterfly-shaped gland at the front of the neck. The hormones it produces influence nearly every organ, which helps explain why thyroid problems can cause symptoms throughout the body.
Hypothyroidism, or underactive thyroid
Hypothyroidism occurs when the thyroid does not make enough thyroid hormone for the body's needs. As hormone levels fall, many body processes can slow down.
According to NIDDK information about hypothyroidism , nearly 5 in 100 Americans age 12 and older have hypothyroidism, although many cases are mild or have few obvious symptoms.
Hashimoto’s disease—an autoimmune disorder in which the immune system attacks and damages the thyroid—is the most common cause of hypothyroidism in the United States. Women and adults over age 60 are more likely to develop hypothyroidism.
Hyperthyroidism, or overactive thyroid
Hyperthyroidism means the thyroid produces more thyroid hormone than the body needs. Instead of slowing down, several body functions may speed up.
Graves’ disease is the most common cause of hyperthyroidism in the United States. It is an autoimmune disease in which antibodies stimulate the thyroid to make excessive amounts of thyroid hormone.
Hashimoto’s disease
Hashimoto’s disease is a common autoimmune thyroid disorder. The immune system mistakenly attacks the thyroid, gradually damaging its ability to produce hormones.
Symptoms may not appear early in the disease. As thyroid function declines, a person may develop the typical signs of hypothyroidism, such as fatigue, cold sensitivity, dry skin, weight gain, constipation, and slower heart rate.
Graves’ disease
Graves’ disease is also autoimmune, but its effect is usually the opposite of Hashimoto’s disease. Instead of reducing thyroid hormone production, antibodies stimulate the thyroid and cause hyperthyroidism.
Graves’ disease can also affect tissues around the eyes. Some people develop Graves’ eye disease, which can cause irritation, swelling, light sensitivity, bulging eyes, pressure, blurred vision, or double vision.
Thyroid nodules and goiter
A thyroid nodule is a lump within the thyroid. A goiter means the thyroid itself has become enlarged.
Many thyroid nodules do not cause symptoms and are found during an examination or imaging performed for another reason. Most nodules are not cancerous, but some need further evaluation based on their size, appearance, growth, symptoms, and other risk factors.
Thyroid cancer
Thyroid cancer begins when abnormal cells grow in thyroid tissue. A neck lump may be a warning sign, but thyroid cancer does not always cause symptoms early.
Thyroid cancer is different from common hormone disorders such as hypothyroidism and hyperthyroidism. Evaluation and treatment depend on the cancer type, its stage, molecular features in some cases, and the person's overall health.
Thyroid disorder | What happens | Possible features |
Hypothyroidism | Too little thyroid hormone is available | Fatigue, cold sensitivity, weight gain, constipation, dry skin, slower heart rate |
Hyperthyroidism | Thyroid activity produces too much hormone | Weight loss, heat sensitivity, sweating, tremor, rapid heartbeat, frequent bowel movements |
Hashimoto’s disease | Autoimmune damage commonly leads to hypothyroidism | Underactive-thyroid symptoms, sometimes goiter |
Graves’ disease | Autoimmune stimulation usually causes hyperthyroidism | Overactive-thyroid symptoms; some people develop eye problems |
Thyroiditis | Thyroid becomes inflamed | Hormone levels may temporarily rise and later fall, depending on the type |
Thyroid nodules | One or more lumps develop in the thyroid | Often no symptoms; some affect hormone production or require cancer evaluation |
Thyroid cancer | Cancerous cells develop in thyroid tissue | May cause a neck lump, hoarseness, or swallowing/breathing problems |
Thyroid symptoms often overlap with everyday problems and other medical conditions. A pattern of symptoms can suggest that thyroid testing is appropriate, but blood tests and, when needed, additional evaluation are what help establish the diagnosis.
What Symptoms Can Thyroid Disorders Cause?
Symptoms depend largely on whether thyroid hormone activity is too low, too high, or normal despite a structural problem such as a nodule. Some symptoms develop gradually and may be easy to overlook.
Symptoms of hypothyroidism
When thyroid hormone levels are too low, body processes tend to slow. Common symptoms can include:
Persistent fatigue
Weight gain
Feeling unusually cold
Dry skin
Dry or thinning hair
Constipation
Joint or muscle discomfort
Slower heart rate
Depression or low mood
Heavy or irregular menstrual periods
Fertility problems
Not everyone develops all these symptoms. Hypothyroidism often develops slowly, sometimes over months or years.
Fatigue and weight gain are also common for many reasons unrelated to the thyroid. They should therefore not be used to self-diagnose hypothyroidism.
Symptoms of hyperthyroidism
Too much thyroid hormone can speed up several body functions. Possible symptoms include:
Unexplained weight loss despite normal or increased appetite
Rapid or irregular heartbeat
Shaky hands or tremor
Nervousness or irritability
Trouble sleeping
Increased sweating
Difficulty tolerating heat
Muscle weakness
Frequent bowel movements
Fatigue
Enlarged thyroid, or goiter
Older adults do not always develop the classic pattern. Hyperthyroidism in an older person may sometimes appear as reduced appetite, weakness, or social withdrawal rather than obvious nervousness or tremor.
Neck and throat symptoms
A thyroid disorder may sometimes cause visible or physical changes in the neck.
These can include:
A new lump or swelling
An enlarged thyroid
Pressure or fullness in the neck
Persistent hoarseness
Trouble swallowing
Difficulty breathing
These symptoms do not automatically mean thyroid cancer. However, a new or changing neck lump deserves medical evaluation.
Body function | Hypothyroidism | Hyperthyroidism |
Energy | Fatigue, sluggishness | Fatigue with restlessness or increased activity |
Weight | Weight gain may occur | Weight loss may occur despite increased appetite |
Temperature | Increased sensitivity to cold | Increased sensitivity to heat and sweating |
Heart | Heart rate may slow | Heart rate may become rapid or irregular |
Bowel habits | Constipation | More frequent bowel movements |
Skin/hair | Dry skin, dry or thinning hair | Skin may feel warm; hair changes can occur |
Mood | Depression or slowed thinking may occur | Nervousness, irritability, or anxiety-like symptoms may occur |
Muscles | Aches or weakness | Weakness or tremor may occur |
Menstrual/fertility health | Heavy or irregular periods and fertility problems can occur | Menstrual and fertility changes can also occur |
Symptoms vary between individuals, and either condition can produce less typical symptoms.
What Causes Thyroid Disorders in the United States?
There is no single cause of thyroid disease. Autoimmune disorders are major causes, but thyroid inflammation, nodules, medicines, previous thyroid treatment, radiation exposure, iodine abnormalities, and other medical conditions can also affect thyroid function.
Autoimmune thyroid disease
Autoimmune disease occurs when the immune system mistakenly reacts against the body's own tissues.
Hashimoto’s disease is the most common cause of hypothyroidism. The immune response damages the thyroid and can gradually reduce hormone production.
Graves’ disease works differently. The immune system produces antibodies that stimulate the thyroid, causing it to make too much thyroid hormone. NIDDK reports that Graves’ disease causes about four out of five cases of hyperthyroidism in the United States.
Family history can matter. Having relatives with Hashimoto’s disease, Graves’ disease, or other autoimmune conditions may be associated with a greater likelihood of developing autoimmune thyroid disease.
Thyroiditis
Thyroiditis means inflammation of the thyroid gland. Depending on its cause and stage, thyroiditis can produce changing thyroid hormone levels.
Inflammation may initially allow stored hormone to leak from the gland, temporarily producing high thyroid hormone levels. The thyroid can subsequently become underactive, and in some people hypothyroidism becomes permanent.
Types include subacute, silent, and postpartum thyroiditis.
Thyroid nodules
Some nodules can produce thyroid hormone independently, resulting in hyperthyroidism. Other nodules do not affect hormone production at all.
Because a thyroid lump cannot reliably be classified by touch or symptoms alone, clinicians may use ultrasound and, when appropriate, fine-needle aspiration biopsy to assess suspicious nodules.
Medicines and previous medical treatment
Certain medicines can affect thyroid hormone production. Previous thyroid surgery, radioactive iodine treatment for hyperthyroidism, and radiation involving the neck can also result in reduced thyroid function.
If the entire thyroid is surgically removed, the body can no longer produce thyroid hormone and replacement therapy is required.
What about iodine?
Iodine is required for thyroid hormone production, but both too little and too much can cause problems in susceptible people.
Iodine deficiency is extremely rare in the United States according to NIDDK. Taking high-dose iodine or seaweed-based supplements without a medical reason is therefore not a general treatment for thyroid disease and may worsen some thyroid conditions.
How Are Thyroid Disorders Diagnosed in the United States?
Thyroid disorders cannot reliably be diagnosed from symptoms alone. Clinicians combine your symptoms and medical history with an examination and laboratory testing, then add imaging or other tests when the suspected condition requires them.
Thyroid blood tests
A common starting point is a thyroid-stimulating hormone, or TSH, blood test. TSH is produced by the pituitary gland and helps regulate thyroid hormone production.
Other tests may measure:
Free T4, or thyroxine
T3, or triiodothyronine, in appropriate situations
Thyroid antibodies when autoimmune disease is suspected
The pattern of TSH and thyroid hormone results helps clinicians determine whether thyroid activity is too low or too high and guides further investigation.
Thyroid ultrasound
Ultrasound uses sound waves to create images of the thyroid. It can help determine a nodule's size and whether it is solid, fluid-filled, or has features that need closer assessment.
Ultrasound can also guide a needle into a nodule when a biopsy is indicated.
Fine-needle aspiration
A fine-needle aspiration, or FNA, removes a small sample of cells from a thyroid nodule. The cells are examined to help determine whether the nodule appears benign, suspicious, malignant, or indeterminate.
Not every thyroid nodule requires biopsy. The decision depends on factors such as ultrasound appearance and size.
Radioactive iodine uptake and thyroid scans
When evaluating certain forms of hyperthyroidism, doctors may use a radioactive iodine uptake test or thyroid scan. These tests can show how actively the thyroid takes up iodine and help distinguish Graves’ disease from overactive nodules and some other causes.
Radioactive iodine testing is not appropriate in every situation, including pregnancy.
What Are the Main Thyroid Disorder Treatment Options?
Treatment depends on the diagnosis rather than symptoms alone. Hypothyroidism generally requires replacement of missing thyroid hormone, while hyperthyroidism may be treated with medication, radioactive iodine, or surgery. Nodules and thyroid cancers require their own risk-based approaches.
Treatment for hypothyroidism
Hypothyroidism is generally treated by replacing thyroid hormone the body can no longer produce adequately.
Levothyroxine is a synthetic form of thyroxine, or T4, that is equivalent to the hormone produced by a healthy thyroid. Treatment is monitored with blood tests so a clinician can determine whether the prescribed amount is maintaining appropriate hormone levels.
Taking excessive thyroid hormone is not harmless. Too much can contribute to problems such as an abnormal heart rhythm or bone loss, so doses should not be changed or stopped without medical guidance.
Certain foods, supplements, and medicines can also affect levothyroxine absorption. People taking thyroid hormone should follow their clinician's or pharmacist's instructions about timing and potential interactions.
Treatment for hyperthyroidism
There is no single treatment that is best for everyone with hyperthyroidism. The cause of the condition, age, symptom severity, pregnancy status, other health conditions, eye disease, medication risks, access to an experienced surgeon, and individual preferences can influence treatment decisions.
The NIDDK guidance on hyperthyroidism treatment describes three major approaches: antithyroid medicines, radioactive iodine therapy, and thyroid surgery.
Antithyroid medicines: These medicines reduce the thyroid's production of new thyroid hormone.
Methimazole is commonly used in the United States, while propylthiouracil has particular uses, including specific pregnancy situations.
Beta-blockers: These medicines may temporarily reduce symptoms such as rapid heartbeat, tremor, and nervousness. They control symptoms rather than stopping thyroid hormone production.
Radioactive iodine: Radioactive iodine-131 is taken by mouth and is absorbed by active thyroid cells, gradually reducing thyroid activity. Many people eventually develop hypothyroidism and then require thyroid hormone replacement. Radioactive iodine is not used during pregnancy or breastfeeding.
Thyroid surgery: Part or all of the thyroid may be surgically removed. Surgery may be considered for reasons including a large goiter, certain nodules, suspected cancer, particular Graves’ disease situations, or when other treatment approaches are unsuitable.
Treatment for thyroid nodules
Treatment depends on what testing shows. Some benign nodules only need monitoring, while others may need treatment because of growth, symptoms, excessive hormone production, or suspicious findings.
Nodules that are cancerous or sufficiently suspicious require specialist evaluation, often involving surgery.
Treatment for thyroid cancer
Thyroid cancer treatment is determined by cancer type and extent. Options may include surgery, radioactive iodine for appropriate thyroid cancers, thyroid hormone therapy, radiation therapy, targeted medicines, or other specialist treatments.
The National Cancer Institute notes that treatment options differ among thyroid cancer types. Some advanced cancers also have molecularly targeted treatments, so management should be individualized by an appropriate cancer and thyroid care team.
Can Lifestyle, Diet, or Supplements Treat a Thyroid Disorder?
Lifestyle habits can support overall health, but they do not replace established treatment for thyroid hormone disorders. A special food, supplement, or restrictive diet should not be assumed to correct Hashimoto’s disease, Graves’ disease, hypothyroidism, hyperthyroidism, a suspicious thyroid nodule, or thyroid cancer.
Be careful with iodine supplements
The thyroid needs iodine, but more iodine does not necessarily mean better thyroid function.
People with Hashimoto’s disease or other autoimmune thyroid disorders may be sensitive to excessive iodine. NIDDK warns that consuming large amounts from sources such as kelp, other seaweeds, or iodine supplements can cause or worsen hypothyroidism in susceptible people.
Ask a healthcare professional before taking an iodine supplement specifically for thyroid health.
Consider medication interactions
Thyroid medicines can interact with foods, supplements, and other medications. For example, the absorption of levothyroxine can be affected by what is taken around the same time.
Rather than changing your medication schedule yourself, ask your pharmacist or healthcare professional how to take it consistently.
Focus on sustainable overall health
A balanced eating pattern, regular physical activity appropriate for your health, adequate sleep, and avoiding tobacco are reasonable parts of general health care. They should complement—not replace—thyroid testing, prescribed medication, monitoring, or specialist treatment when these are needed.
When Should You Seek Medical Care for Possible Thyroid Problems?
Arrange a medical evaluation if you develop persistent symptoms that could fit a thyroid problem, particularly when several occur together. Examples include unexplained weight changes, persistent fatigue, ongoing heat or cold intolerance, significant changes in heart rate, menstrual changes, or a new neck lump.
Seek prompt medical attention for a rapidly worsening or irregular heartbeat, significant breathing difficulty, severe weakness, confusion, or other serious symptoms. Severe uncontrolled hyperthyroidism can rarely progress to thyroid storm, while severe untreated hypothyroidism can rarely lead to myxedema coma; both are medical emergencies.
A new neck mass, persistent hoarseness, or increasing trouble swallowing or breathing should also be evaluated. The National Cancer Institute information on thyroid cancer identifies a neck lump, trouble breathing or swallowing, pain with swallowing, and hoarseness among possible warning signs, although these symptoms can have noncancerous causes.
People who are pregnant or planning pregnancy should discuss known or suspected thyroid disease with their healthcare professional. Thyroid hormone needs and treatment considerations can change during pregnancy, making appropriate testing and monitoring especially important.
People taking antithyroid medicines should follow their clinician's safety instructions carefully. Fever or a persistent sore throat while taking an antithyroid medicine requires prompt medical advice because, rarely, these medicines can cause a serious reduction in infection-fighting white blood cells.
Conclusion
Understanding thyroid disorders in the United States starts with recognizing that hypothyroidism, hyperthyroidism, Hashimoto’s disease, Graves’ disease, thyroid nodules, and thyroid cancer are different conditions that require different approaches. Symptoms such as fatigue, weight changes, temperature intolerance, heart-rate changes, or neck swelling can provide clues, but they cannot establish a diagnosis on their own. Blood tests and appropriate follow-up are essential.
Most thyroid conditions have established management options, and treatment is chosen according to the cause and individual circumstances. If symptoms persist, a neck lump appears, or you already take thyroid medication, seek appropriate medical guidance rather than changing treatment or using thyroid supplements on your own.
Frequently Asked Questions
1 . What are the first signs of a thyroid problem?
Early signs can include unexplained fatigue, weight changes, unusual sensitivity to heat or cold, bowel changes, or changes in heart rate. Symptoms vary considerably between people. Because these problems have many possible causes, thyroid blood tests are usually needed to determine whether thyroid function is abnormal.
2 . How can I tell if my thyroid is underactive or overactive?
Symptoms can suggest a pattern, but you cannot reliably distinguish the conditions yourself. Hypothyroidism often causes cold sensitivity, constipation, and sluggishness, while hyperthyroidism can cause heat sensitivity, tremor, and rapid heartbeat. TSH and thyroid hormone blood tests help establish which problem is present.
3 . Is Hashimoto’s disease the same as hypothyroidism?
No, although Hashimoto’s disease commonly causes hypothyroidism. Hashimoto’s is an autoimmune disease that damages the thyroid, whereas hypothyroidism describes the state of having insufficient thyroid hormone. Other conditions and treatments can also cause hypothyroidism.
4 . Can thyroid disorders cause weight gain or weight loss?
Yes, thyroid hormone abnormalities can affect body weight, but weight changes alone do not prove thyroid disease. Hypothyroidism may contribute to weight gain, while hyperthyroidism may cause weight loss despite increased appetite. Many other health, medication, dietary, and lifestyle factors also influence weight.
5 . Do all thyroid nodules mean cancer?
No, most thyroid nodules are not cancerous. Doctors assess nodules using factors such as physical examination, thyroid tests, ultrasound features, size, and sometimes fine-needle aspiration. A new or changing neck lump should still be evaluated rather than assumed to be harmless.
6 . Can a thyroid disorder be permanently cured?
It depends on the disorder and treatment used. Some thyroid problems are temporary, while chronic hypothyroidism often requires long-term hormone replacement, and definitive hyperthyroidism treatment may lead to permanent hypothyroidism. Treatment goals and long-term monitoring therefore depend on the underlying diagnosis.
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