Thyroiditis

Thyroiditis is inflammation of your thyroid gland. Your thyroid is a small, butterfly-shaped gland located at the front of your neck under your skin. It’s a part of your endocrine system and controls many of your body’s important functions by producing and releasing certain hormones.

Thyroiditis includes a group of individual conditions that cause thyroid inflammation but have different causes and symptoms. Thyroiditis can lead to over- or under-production of thyroid hormone.

In most types of thyroiditis, there are three phases, including:

Thyrotoxic phase: During this phase, your thyroid is inflamed and releases too many hormones, causing temporary thyrotoxicosis.

Hypothyroid phase: Following the excessive release of thyroid hormones for a few weeks or months, your thyroid won’t have enough thyroid hormones to release. This leads to a lack of thyroid hormones or hypothyroidism. Hashimoto’s thyroiditis and radiation-induced thyroiditis usually permanently stay in the hypothyroid phase.

Euthyroid phase: During the euthyroid phase, your thyroid hormone levels are normal. This phase may come temporarily after the thyrotoxic phase before going to the hypothyroid phase, or it may come at the end after your thyroid gland has recovered from the inflammation and can maintain a normal hormone level.

Types of thyroiditis include:

Hashimoto’s thyroiditis: This autoimmune condition, also called chronic lymphocytic thyroiditis, is caused by antithyroid antibodies. It’s the most common form of thyroiditis and the most common cause of hypothyroidism.

Silent or painless thyroiditis: This is an autoimmune condition caused by antithyroid antibodies.

Postpartum thyroiditis: This is an autoimmune condition caused by antithyroid antibodies that can occur within one year after giving birth. It’s relatively rare.

Radiation-induced thyroiditis: This is a condition caused by radiation therapy used as a medical treatment for certain cancers or by radioactive iodine used to treat hyperthyroidism.

Subacute thyroiditis or de Quervain’s thyroiditis: This is an often painful condition thought to be caused by a virus. It’s usually preceded by upper respiratory infections.

Acute infectious thyroiditis: This is a rare condition caused by an infectious organism or bacterium.

Drug-induced thyroiditis: This is a condition caused by the use of medications such as amiodarone, interferons, lithium and cytokines. It only occurs in a small fraction of people using these drugs.

Riedel thyroiditis: This is a rare disease caused by chronic inflammation and fibrosis of your thyroid gland. Fibrosis is the thickening or scarring of tissue.

The symptoms of thyroiditis depend on the type of thyroiditis and its phase. Most types of thyroiditis cause thyrotoxicosis symptoms followed by hypothyroid symptoms.

Subacute thyroiditis and acute infectious thyroiditis usually also cause pain in your thyroid area. Some people with thyroiditis have an enlarged thyroid gland (goiter).

Symptoms of thyrotoxicosis

The thyrotoxic phase of thyroiditis is usually short, lasting one to three months. If your thyroid cells are damaged quickly and there’s a leak of excess thyroid hormone, you might experience symptoms of hyperthyroidism (overactive thyroid), which include:

Fast heart rate.

Increased appetite.

Unexplained weight loss.

Anxiety and nervousness.

Irritability.

Trouble sleeping

Increased sweating and sensitivity to heat.

Tremors.

Symptoms of hypothyroidism

The hypothyroid phase of thyroiditis can be long-lasting and may become permanent. If your thyroid cells are damaged and thyroid hormone levels fall, you might experience the symptoms of hypothyroidism, which include:

Fatigue.

Unexplained weight gain.

Constipation.

Depression.

Dry skin.

Increased sensitivity to cold.

Muscle weakness.

Decreased ability to concentrate and focus.

Thyroiditis is caused by an attack on your thyroid, causing inflammation (your body’s response to an injury) and damage to the thyroid cells. It has several different causes depending on the type.

The most common cause, or “attacker,” is an autoimmune disease, which is the result of your immune system accidentally attacking your body instead of protecting it. It's unclear why your immune system does this. Antibodies that attack your thyroid cause most types of thyroiditis.

This chart lists the causes for each type of thyroiditis.

Type of thyroiditis Cause

Hashimoto’s thyroiditis Antithyroid antibodies, autoimmune disease.

Silent or painless thyroiditis Antithyroid antibodies, autoimmune disease.

Postpartum thyroiditis Antithyroid antibodies, autoimmune disease.

Subacute thyroiditis (de Quervain’s thyroiditis) Likely a virus.

Acute infectious thyroiditis Most commonly bacteria, but any infectious organism.

Radiation-induced thyroiditis Follows treatment with radioactive iodine for hyperthyroidism or external beam radiation therapy for certain cancers.

Drug-induced thyroiditis Certain medications, including amiodarone, lithium, interferons, interleukin-2 and checkpoint inhibitors.

Riedel thyroiditis Fibrosis (thickening and scarring) of your thyroid.

Sex. Women are much more likely to get Hashimoto's disease.

Age. Hashimoto's disease can occur at any age but more commonly occurs during middle age.

Other autoimmune disease. ...

Genetics and family history. ...

Pregnancy. ...

Excessive iodine intake. ...

Radiation exposure.

Goiter. Constant stimulation of your thyroid to release more hormones may cause the gland to become larger — a condition known as a goiter. Although generally not uncomfortable, a large goiter can affect your appearance and may interfere with swallowing or breathing.

Heart problems. Hypothyroidism may also be associated with an increased risk of heart disease and heart failure, primarily because high levels of low-density lipoprotein (LDL) cholesterol — the "bad" cholesterol — can occur in people with an underactive thyroid.

Mental health issues. Depression may occur early in hypothyroidism and may become more severe over time. Hypothyroidism can also cause slowed mental functioning.

Peripheral neuropathy. Long-term uncontrolled hypothyroidism can cause damage to your peripheral nerves. These are the nerves that carry information from your brain and spinal cord to the rest of your body — for example, your arms and legs. Peripheral neuropathy may cause pain, numbness and tingling in affected areas.

Myxedema. This rare, life-threatening condition is the result of long-term, undiagnosed hypothyroidism. Its signs and symptoms include intense cold intolerance and drowsiness followed by profound lethargy and unconsciousness.

A myxedema coma may be triggered by sedatives, infection or other stress on your body. If you have signs or symptoms of myxedema, you need immediate emergency medical treatment.

Infertility. Low levels of thyroid hormone can interfere with ovulation, which impairs fertility. In addition, some of the causes of hypothyroidism — such as autoimmune disorder — can also impair fertility.

Birth defects. Babies born to women with untreated thyroid disease may have a higher risk of birth defects compared to babies born to healthy mothers. These children are also more prone to serious intellectual and developmental problems.

Infants with untreated hypothyroidism present at birth are at risk of serious problems with both physical and mental development. But if this condition is diagnosed within the first few months of life, the chances of normal development are excellent.

Unfortunately, most cases of thyroiditis can’t be prevented.

If you have a condition that requires treatment using radioactive iodine or radiation therapy, talk to your healthcare provider about your risk of thyroiditis. You may be able to start with other treatments to avoid developing thyroiditis.

If you take prescription drugs that can cause thyroiditis, talk to your provider about your risk and if you can stop taking them. You still may not be able to avoid thyroiditis.