Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormones. An underactive thyroid gland can lead to weight gain, tiredness, and feeling cold constantly.

Thyroid hormones (thyroxine) regulate metabolism, which is how the body uses energy. If thyroxine levels are low, many of the body’s functions slow down.

About 4.6% of the population of the United States of America ages 12 years and above have hypothyroidism.

The thyroid gland is found in the front of the neck below the larynx, or voice box, and has two lobes, one on each side of the windpipe.

The production of thyroid hormones is regulated by thyroid-stimulating hormone (TSH), which is made by the pituitary gland.

This, in turn, is regulated by the hypothalamus, a region of the brain. TSH ensures that enough thyroid hormones are made to meet the needs of the body.

This article discusses the symptoms, causes, treatments, and risk factors of hypothyroidism.

Fast facts on hypothyroidism

  • The thyroid gland produces two thyroid hormones, T3 and T4.
  • These hormones regulate the body’s metabolism.
  • The most common cause of hypothyroidism in the U.S. is Hashimoto’s disease.
  • Symptoms of hypothyroidism include fatigue, cold intolerance, and joint and muscle pain.
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Thyroid hormones affect multiple organ systems, so the symptoms of hypothyroidism are wide-ranging and diverse.

The thyroid creates two thyroid hormones, triiodothyronine (T3) and thyroxine (T4). These regulate metabolism, and they also affect the following functions:

  • brain development
  • breathing
  • heart and nervous system functions
  • body temperature
  • muscle strength
  • skin dryness
  • menstrual cycles
  • weight
  • cholesterol levels

While the symptoms of hypothyroidism can vary, common symptoms include:

If left untreated, the following symptoms can manifest:

If it develops in children or teenagers, the signs and symptoms are generally the same as in adults.

However, they may also experience:

  • poor growth
  • delayed development of teeth
  • poor mental development
  • delayed puberty

Hypothyroidism develops slowly. Symptoms may go unnoticed and they may be vague and general.

Symptoms vary between individuals, and they are shared by other conditions. The only way to obtain a concrete diagnosis is through a blood test.

Read more about symptoms of hypothyroidism.

FDA Drug safety recall warning

Certain brands and strengths of medication for hypothyroidism (underactive thyroid) have been recalled. This is due to the medication having less active drug (levothyroxine) than they are supposed to.

Taking these tablets can lead to inadequately treated hypothyroidism, which manifests in the symptoms people experience, such as fatigue, constipation, hair loss, and depression. Reduced effectiveness can be particularly dangerous for older people and those who are pregnant.

Call your pharmacist to find out if your medication has been recalled. Do not stop taking the medication unless advised to do so by your healthcare professional.

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Treatment for hypothyroidism focuses on supplementing the thyroid hormone. At present, there is no cure for hypothyroidism. However, symptoms can be managed in most cases.

Synthetic thyroxine

To replenish levels, doctors usually prescribe synthetic thyroxine (levothyroxine), a medication that is identical to the T4 hormone. Doctors may recommend taking this in the morning before eating each day.

Dosage is determined by the individual’s history, symptoms, and current TSH level. Healthcare professionals will regularly monitor the person’s blood to determine if the dosage of synthetic T4 needs to be adjusted.

Regular monitoring will be required, but the frequency of blood tests will likely decrease over time.

Iodine and nutrition

Iodine is an essential mineral for thyroid function. Iodine deficiency is one of the most common causes of goiter development, or abnormal enlargement of the thyroid gland.

However, iodine deficiency is rare in the U.S.

Maintaining adequate iodine intake is important for most people, but those with autoimmune thyroid disease can be particularly sensitive to the effects of iodine, meaning that it can trigger or worsen hypothyroidism. They should inform their doctor if they are sensitive to the effects of iodine.

During pregnancy, iodine requirements increase. Using iodized salt in the diet and taking prenatal vitamins can maintain the required levels of iodine.

Hypothyroidism can typically be managed appropriately by following the advice of a qualified healthcare professional. With appropriate treatment, thyroid hormone levels should return to normal.

In most cases, medications for hypothyroidism will need to be taken for the rest of the person’s life.

There is no way to prevent hypothyroidism. However, some people may be more at risk of developing the condition than others.

People with the following factors may wish to ask their healthcare professional about checking their thyroid levels:

  • a history of autoimmune disease
  • previous radiation treatment to the head or neck
  • a goiter
  • family history of thyroid problems
  • use of medications known to affect thyroid function

There are no specific diet recommendations for hypothyroidism. However, individuals should follow a varied, well-balanced diet that is not high in fat or sodium.

Consuming additional iodine can interfere with the balance involved in treatment. Any changes to diet or supplementation should be discussed with a healthcare professional.

Learn more about foods to eat and avoid with hypothyroidism.

Hypothyroidism occurs when the thyroid gland is unable to produce adequate levels of thyroid hormones. There are various conditions and factors that can lead to the development of hypothyroidism.

Hashimoto’s thyroiditis

The most common cause of hypothyroidism in the U.S. is Hashimoto’s thyroiditis, also known as chronic lymphocytic thyroiditis or autoimmune thyroiditis.

Hashimoto’s thyroiditis is an autoimmune disease, a disorder in which the immune system attacks the body’s own cells and organs.

The condition causes the immune system to attack the thyroid gland, leading to inflammation and interfering with its ability to produce thyroid hormones.

Learn more about Hashimoto’s thyroiditis.


Thyroiditis is an inflammation of the thyroid gland. It causes thyroid hormones to leak into the blood, raising their overall levels and leading to hyperthyroidism. After 1 to 2 months, this may develop into hypothyroidism.

Thyroiditis can be the result of viral or bacterial infection, an autoimmune condition, or following pregnancy.

Congenital hypothyroidism

In cases of congenital hypothyroidism, the thyroid gland does not function properly from birth.

This can lead to physical and mental growth problems, but early treatment can prevent these complications. Most newborns in the U.S. are screened for hypothyroidism.

Learn more about congenital hypothyroidism.

Thyroid surgery and iodine treatment

Thyroid iodine treatment and surgery can lead to hypothyroidism.

Several conditions such as hyperthyroidism, goiters, thyroid nodules, and thyroid cancer can be treated by partially or fully removing the thyroid gland. This may result in hypothyroidism.

Radiation treatment of the thyroid can also lead to hypothyroidism. Radioactive iodine is a common treatment for hyperthyroidism. It works by destroying the cells of the thyroid gland and decreasing the production of thyroid hormone.

Radiation is also used to treat people with head and neck cancers, Hodgkin’s disease, and other lymphomas, which can lead to damage to the thyroid gland.


Certain medications may interfere with thyroid hormone production. These include:

Pituitary gland abnormalities

If the pituitary gland stops functioning properly, the thyroid gland may not produce the correct amount of thyroid hormone.

Pituitary tumors or pituitary surgery can affect the function of the pituitary gland, and this can adversely affect the thyroid gland.

Sheehan syndrome is a rare condition that involves damage to the pituitary gland. If a person loses a life threatening amount of blood or has severely low blood pressure during or after childbirth, the gland can be damaged, causing it to under-produce pituitary hormones.

Healthcare professionals usually perform a physical examination and take a medical history. They then typically request blood tests.

The most common blood test is the TSH test. This detects the amounts of TSH in the blood.

If the TSH reading is above normal, the patient may have hypothyroidism. If TSH levels are below normal, the patient may have hyperthyroidism or hypothyroidism.

The T3, T4, and thyroid autoantibody tests are additional blood tests used to confirm the diagnosis or determine its cause.

The doctor may run a complete thyroid panel, testing levels of T3 and T4, TSH, and thyroid autoantibodies in order to fully establish the health and activity of the thyroid gland.

There may also be tests to check cholesterol levels, liver enzymes, prolactin, and sodium.

Learn more about the TSH test.

Certain conditions and medications may make it more likely for a person to develop hypothyroidism.

People may have a greater risk of developing a thyroid disorder if they have conditions such as Turner syndrome or autoimmune diseases like lupus or rheumatoid arthritis.

The risk of hypothyroidism is also higher in people with a family history of thyroid disease and those over the age of 60.

Hypothyroidism is also more likely to affect people who were assigned female at birth.

During and after pregnancy

Increased demands on metabolism during pregnancy can result in increased demands on the thyroid.

If hypothyroidism occurs during pregnancy, it is usually due to Hashimoto’s thyroiditis. This condition affects between 2-3% of pregnant people.

Uncontrolled hypothyroidism increases the risk of miscarriage, preterm delivery, and a rise in blood pressure during late pregnancy, or preeclampsia.

Below are some commonly asked questions.

What are the top 10 signs of hypothyroidism?

The following are 10 signs of hypothyroidism:

  1. fatigue
  2. weight gain
  3. cold intolerance
  4. joint and muscle pain, cramps, and weakness
  5. constipation
  6. dry skin
  7. thin, brittle hair or fingernails
  8. decreased sweating
  9. pins and needles
  10. heavy periods, or menorrhagia

What happens to a person with hypothyroidism?

A person with hypothyroidism will likely feel tired, depressed, and gain weight. However, a person can take daily hormone tablets to replace the hormones their thyroid is not making and the condition can be successfully treated.

Hypothyroidism does not appear to negatively impact a person’s life expectancy. In fact, a 2017 study suggests people with low-normal thyroid function lived up to 3.5 years longer overall compared with people with high-normal thyroid function.

What is usually the first symptom of hypothyroidism?

As hypothyroidism develops slowly, a person may not notice symptoms of the disease for months or even years. However, the most common symptoms in adults are fatigue, lethargy, cold intolerance, weight gain, constipation, change in voice, and dry skin.

Hypothyroidism occurs when the thyroid gland is unable to produce an adequate amount of thyroid hormones.

Symptoms of hypothyroidism can vary from person to person. They can include fatigue, weight gain, and joint or muscle pain.

Treatment for hypothyroidism involves medications to replace the thyroid hormones. Typically, people with hypothyroidism need to take medications for life.

If a person experiences symptoms of hypothyroidism, they should speak with a healthcare professional.