The thyroid is a butterfly-shaped gland that sits in the front of the neck. It produces hormones that are essential for heart rate, digestion, mood, and other functions crucial to human health.

The thyroid produces the hormones calcitonin, thyroxine (T4), and triiodothyronine (T3). These hormones keep body processes, including metabolism, mood, breathing, and heart rate, running smoothly.

Diseases such as Hashimoto’s thyroiditis cause a hormone imbalance, disrupting the thyroid gland’s hormone production to varying degrees.

The American Thyroid Association estimates that more than 12% of people in the United States experience some form of thyroid issue during their lifetime. Around 60% of people with thyroid disease do not know they have the condition.

This article looks at the thyroid gland, its functions, and some common conditions that can cause thyroid disease.

A person holding their neck, which is where the thyroid gland is.Share on Pinterest
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The thyroid gland resides in the neck just above the collarbone. It is a type of endocrine gland, meaning it makes hormones. The thyroid resembles a butterfly with a right and left lobe on either side of the windpipe.

Click on the BodyMap above to interact with a 3D model of the thyroid gland.

The thyroid uses iodine to produce hormones that affect:

  • breathing
  • heart rate
  • digestion
  • weight
  • moods

The three hormones that the thyroid produces are:

  • calcitonin
  • T3
  • T4

Iodine is the main component of T3 and T4 hormones. However, the body does not produce iodine naturally, so it is essential to consume it through the diet.

The purpose of T3 and T4 hormones is to increase the basal metabolic rate or number of calories the body needs to function at a resting state.

Cells called c-cells make calcitonin which assists in calcium and bone metabolism.

When the body needs lower or higher levels of these hormones, the pituitary gland signals the thyroid gland to change the production level.

Various conditions can affect the thyroid gland, and thyroid disease can develop when the thyroid makes too much or too little calcitonin, T3, and T4.


Hyperthyroidism occurs when the thyroid produces too much calcitonin, T3, and T4.

People with a higher risk of hyperthyroidism include women, anyone older than 60 years, and anyone pregnant in the past 6 months.

Hyperthyroidism risk is also higher in people who have had:

Symptoms of hyperthyroidism include:

  • nervousness
  • irritability
  • muscle weakness
  • inability to tolerate heat
  • fatigue
  • trouble sleeping
  • hand tremor
  • rapid, irregular heartbeat
  • diarrhea
  • weight loss
  • mood swings

Hyperthyroidism treatment involves anti-thyroid or beta-blocker medication, radioiodine therapy, or surgery.

If doctors do not treat the condition, hyperthyroidism can cause serious heart, muscle, bone, fertility, and menstrual cycle problems.


Hypothyroidism is the opposite of hyperthyroidism and occurs when the thyroid does not produce enough of the hormones calcitonin, T3, and T4.

Those at a higher risk for hypothyroidism include women, anyone over 60 years, and those who have had any of the following:

Symptoms of hypothyroidism include:

  • fatigue
  • weight gain, puffy face
  • inability to tolerate cold
  • muscle and joint pain
  • constipation
  • dry skin
  • dry, thinning hair
  • irregular or heavy menstrual periods
  • fertility problems in females
  • depression
  • slow heart rate
  • goiter

Hypothyroidism treatment includes medication to substitute the hormone the thyroid is not producing. After 6–8 weeks of treatment, doctors use a blood test to check that the person is receiving the correct dose.

Thyroid cancer

Thyroid cancer is a disease where cancer cells form in the tissue of the thyroid gland.

Risk factors include:

  • being 25–65 years
  • being female
  • exposure of the head and neck to radiation
  • history of goiter
  • family history of thyroid disease or thyroid cancer
  • genetic conditions, such as multiple endocrine neoplasia syndromes
  • being Asian

Thyroid cancer may not have any symptoms in the early stages. However, as the tumor grows, the individual may develop:

  • trouble swallowing
  • pain when swallowing
  • a lump in the neck
  • trouble breathing
  • hoarseness

Treatment for thyroid cancer depends on the stage and the type that a person has. Potential treatment options include:


Thyroiditis refers to inflammation of the thyroid gland. There is no single uniform presentation unique to thyroiditis. Instead, it causes other thyroid conditions, such as hyperthyroidism, hypothyroidism, and thyrotoxicosis.

Treatment depends on the cause.

Hashimoto’s thyroiditis

Hashimoto’s thyroiditis is an autoimmune disorder involving chronic inflammation of the thyroid. If Hashimoto’s thyroiditis develops into hypothyroidism, the individual may experience:

  • weight gain
  • fatigue
  • constipation
  • increase in sensitivity to cold
  • depression
  • dry skin
  • muscle aches

Treatment for hypothyroidism involves taking medication to replace thyroid hormones.

Individuals with Hashimoto’s thyroiditis need to complete a blood test every 6–8 weeks until their doctor can determine the correct dosage for the medication.

Grave’s disease

Grave’s disease is an autoimmune condition that results in hyperthyroidism. It is one of the most common conditions that lead to hyperthyroidism, affecting roughly 1 in 200 people. It most often affects women under 40 years but can also affect men.

Previously, people may have referred to the condition as exophthalmic goiter, but now the condition takes the name of Sir Robert Graves, an Irish doctor who first described the condition in 1835.

Thyroid nodules

A thyroid nodule is a lump that may appear on the thyroid gland. It may feel like a bump in the middle or side of the throat. Thyroid nodules are relatively common, affecting roughly 20–76% of adults in the U.S.

A nodule can develop for different reasons. It may be a cyst, a sign of iodine deficiency, or, in some cases, thyroid cancer.

Toxic multinodular goiter

A goiter is a term that refers to an enlarged thyroid gland. In some cases, a person may have a multinodular goiter. When the thyroid gland produces too much thyroid hormone, causing hyperthyroidism, people may refer to it as a toxic multinodular goiter.

It is difficult to prevent thyroid gland disease, as it is not possible to modify some of the known risk factors, such as genetics. However, people can take certain measures to reduce the likelihood.

The main way to reduce the risk of developing hypothyroidism is to consume enough iodine. Because the body does not naturally produce iodine, people must eat food containing iodine or take dietary supplements. However, consuming too much iodine can aversely affect the T3 and T4 hormones.

People should also avoid smoking if they have concerns about thyroid disease, as cigarette smoke can affect iodine uptake.

If an individual has a family history of thyroid disease, they should have regular blood work to monitor their thyroid hormone levels and ensure they remain within an acceptable range.

Anyone experiencing symptoms of hyperthyroidism or hypothyroidism should visit a doctor to review their hormone levels. People should also contact their doctor if they can feel a new lump in their neck or experience any symptoms affecting their throats, such as difficulty eating or breathing.

Doctors can diagnose thyroid diseases through:

  • physical examination
  • medical history
  • thyroid tests
  • biopsy

Thyroid tests include TSH, T3, T4, and thyroid antibody blood tests, and imaging tests such as:

The thyroid gland is a hormone-producing gland located just above the collarbone. It produces T3, T4, and calcitonin, which help with metabolism, calcium production, and bone metabolism.

When the thyroid gland does not work correctly, it can cause hyperthyroidism, hypothyroidism, thyroid cancer, thyroiditis, and Hashimoto’s thyroiditis.

It is not possible to prevent thyroid disease entirely, but a person can reduce the chance of developing it by consuming an adequate amount of iodine. People should also avoid tobacco smoke.

Anyone with a family history of thyroid problems should visit a doctor regularly to ensure that their hormone levels are within an acceptable range.