Primary hypothyroidism typically occurs due to damage to the thyroid. Symptoms can range from mild to severe and may include weight gain and tiredness.

Hypothyroidism is a condition in which the body does not produce enough thyroid hormones.

About 5% of people in the United States currently live with hypothyroidism. Primary hypothyroidism is the more common form of this condition.

The symptoms of primary hypothyroidism can range in severity from mild to severe. Symptoms may include tiredness, constipation, weight gain, and depression. Medications that replace thyroid hormones can help reduce or resolve these symptoms in most cases.

This article further explains primary hypothyroidism. It discusses what causes the condition, its symptoms, and how to treat it.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Primary hypothyroidism is a more common form of hypothyroidism. This condition occurs after damage to the thyroid gland occurs. This damage may happen as a result of an autoimmune condition, or it may happen following a medical procedure such as surgery or radiation.

The thyroid is a gland located at the front of the throat. This gland produces hormones that are crucial for typical body functions. Thyroid hormones are especially important for supporting metabolic processes.

Metabolic processes refer to the body’s metabolism. This includes the reactions that occur in the body to create and provide energy.

With hypothyroidism, the thyroid gland does not produce enough of these hormones. This affects all other parts of the body and can cause many body functions to slow down.

The symptoms of primary hypothyroidism will differ from person to person. Some of the more common symptoms of this condition may include:

Research suggests that primary hypothyroidism can cause depression in some people. This may occur because of the metabolic effects of the condition.

Metabolic processes in the brain are important for supporting cognitive function and mental health. Primary hypothyroidism disrupts metabolic processes. This may lead to mental health effects such as depression.

Primary hypothyroidism may occur for a variety of reasons. Examples include:

  • dietary deficiencies
  • certain medications
  • thyroid surgery
  • autoimmune conditions

Iodine deficiency

In order to make thyroid hormones, the thyroid gland requires iodine. This mineral occurs naturally in foods such as fish, eggs, dairy products, and iodized salt. Certain dietary supplements also contain this important mineral.

When a person does not consume enough iodine, their body cannot produce enough thyroid hormones. In these cases, iodine deficiency may ultimately lead to primary hypothyroidism.

Females have an overall higher risk of developing iodine deficiency. Taking iodine supplements can help treat this deficiency and prevent further health complications. A person can speak with a doctor to learn more about helping to prevent or treat iodine deficiency.

Learn about iodine-rich foods.

Certain medical treatments

Research has indicated that certain medications can cause primary hypothyroidism. These include:

Certain medical procedures can also cause primary hypothyroidism. Such procedures include radiation therapy to the head or neck, thyroid surgery, or thyroid radioactive iodine therapy.

Other causes

In addition to iodine deficiency and certain medical treatments, autoimmune conditions can also cause primary hypothyroidism. Chronic autoimmune thyroiditis is the most common of these conditions.

Individuals with chronic autoimmune thyroiditis produce higher levels of antithyroid antibodies. These antibodies may harm the thyroid gland in certain cases. In time, this damage can lead to primary hypothyroidism.

A person can speak with a healthcare professional to learn more about autoimmune conditions and other causes of primary hypothyroidism.

To diagnose primary hypothyroidism, a doctor may begin with a physical exam. During this exam, they will determine whether an individual is experiencing symptoms of this condition. These symptoms can include fatigue, constipation, dry skin, and mood changes.

If an individual shows signs of primary hypothyroidism, a doctor will typically order blood tests. These tests determine the levels of thyroid hormones in the body.

A doctor may order different tests depending on individual circumstances. Generally, they order tests to determine the levels of thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) in a person’s body.

Thyroid-stimulating hormone

TSH is an important hormone because it instructs the thyroid on how much thyroid hormone to produce. When the thyroid does not produce enough thyroid hormones, the level of TSH rises. Because of this, a high TSH level may indicate primary hypothyroidism.

Learn about TSH testing.

Triiodothyronine and thyroxine

The thyroid produces the T3 and T4 hormones. These hormones both help the body expend energy. They are crucial for regulating body temperature, weight, and other functions. Low T3 or T4 levels may be a sign of primary hypothyroidism.

If levels of TSH, T3, or T4 fall outside the typical ranges, a doctor may diagnose primary hypothyroidism.

The main treatment option for primary hypothyroidism is levothyroxine. This medication helps replace hormones that the thyroid cannot produce.

A doctor typically prescribes levothyroxine treatment with a low starting dose. They will then continue to monitor the person and make dose adjustments over time as needed.

Many people experience symptom relief with levothyroxine, although it may not be suitable for everyone. For instance, the thyroid hormones levothyroxine helps produce can have serious effects on heart function. This means the medication may not be appropriate for those with a heart condition.

Individuals with primary hypothyroidism should speak with a healthcare professional to learn more about treatment options.

The following are some questions people frequently ask about primary hypothyroidism.

What is the difference between hypothyroidism and primary hypothyroidism?

Primary hypothyroidism occurs when the thyroid gland cannot produce enough thyroid hormones. Secondary hypothyroidism occurs when the thyroid gland functions correctly but the pituitary gland or hypothalamus does not.

Secondary hypothyroidism may happen as a result of tumors in the pituitary gland or hypothalamus. Radiation therapy, certain medications, or other health conditions may also play a role.

Is primary hypothyroidism serious?

Many people with primary hypothyroidism can lead full, otherwise typical lives with treatment. However, some people may continue to experience symptoms even after treatment.

In certain cases, primary hypothyroidism can increase the risk of serious health complications. These include heart disease, coronary artery disease, and stroke. Seeking a diagnosis and prompt treatment can help reduce the risk of these and other complications.

What is the main cause of primary hypothyroidism?

There is no single cause of primary hypothyroidism, as the cause can vary between individuals. Some common causes include iodine deficiency, certain medications, and a history of thyroid surgery.

Individuals with this condition can speak with a doctor to learn more.

Primary hypothyroidism occurs when the thyroid cannot produce enough thyroid hormones. These hormones are important for maintaining the body’s metabolic processes.

Individuals with this condition may experience symptoms such as tiredness, weight gain, constipation, and muscle pain. People experiencing these or other symptoms should visit a healthcare professional for an evaluation.

With an accurate diagnosis and prompt treatment, it is possible to manage the symptoms of primary hypothyroidism.