What are the other Names for this Condition? (Also known as/Synonyms)

• Thyroiditis caused by Radiation Treatment
• Thyroiditis from Radiation Treatment
• Radiation Thyroiditis

What is Radiation-Induced Thyroiditis? (Definition/Background Information)

• Thyroiditis is an inflammation of the thyroid gland from various causes, which results in a set of associated signs and symptoms. Radiation-Induced Thyroiditis occurs secondary to radiation therapy, resulting in inflammation and scarring of the thyroid gland
• The external radiation may be administered to treat certain head and neck cancers or hyperthyroidism (which develops from Graves’ disease). The magnitude of injury to the thyroid depends on the duration, dose, and type of radiation given
• Radiation-Induced Thyroiditis may either result in an overactive or underactive thyroid gland with associated presentations. The signs and symptoms may also include pain, tenderness, and swelling of the thyroid gland
• The treatment of Radiation-Induced Thyroiditis may include medications for pain and inflammation, along-with a management of abnormal thyroid hormone levels. The prognosis is generally good, but may vary from one individual to another, and depends on several factors

Who gets Radiation-Induced Thyroiditis? (Age and Sex Distribution)

• Radiation-Induced Thyroiditis is a rare form of thyroiditis; only a small percentage of the individuals administered radiation for various reasons develop this condition
• Both males and females can be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Radiation-Induced Thyroiditis? (Predisposing Factors)

The risk factors for Radiation-Induced Thyroiditis may include:

• Radiation therapy (low-dose) to treat certain forms of lymphomas and malignancies involving the head and neck region
• Radioactive iodine (I-131) therapy; nuclear medicine treatment for Graves' disease or thyroid cancer
• Radioactive therapy to treat thyroid gland dysfunction such as hyperthyroidism
• Accidental or occupational exposure to high-dose radiation

The condition may be influenced by contributory factors such as:

• Younger age of the individual
• Female gender
• Dosage and duration of radiation
• Pre-existing hyperthyroidism or hypothyroidism

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Radiation-Induced Thyroiditis? (Etiology)

• Radiation-Induced Thyroiditis typically develops due to damage sustained by the thyroid gland following radiation therapy
• This may occur following radiation treatment for various illnesses including throat cancers, lymphomas, and Graves’ disease
• According to some reports, the condition is known to develop about 5-10 days following radiation treatment

What are the Signs and Symptoms of Radiation-Induced Thyroiditis?

The signs and symptoms of Radiation-Induced Thyroiditis may vary from one individual to another. It may be mild or severe and related to the dose, duration, type, and method of radiation therapy administered. The onset of signs and symptoms may be noted within 1-2 weeks of radiation exposure. Either increased or decreased hormone secretions may be noted, resulting in hyperthyroidism or hypothyroidism respectively.

The signs and symptoms may include:

• Pain
• Tenderness
• Swelling of the thyroid gland
• Worsening of hyperthyroidism if present

The associated signs and symptoms of hyperthyroidism may include:

• Sleeping difficulties including insomnia
• Excess sweating and intolerance to heat
• Increased to excessive hunger
• Irritation, restlessness, and nervousness
• Protrusion of the eyes
• Menstrual abnormalities in women; menstruation may be irregular or short
• Abnormal heartbeat rate including rapid heart rate
• Weight loss

The signs and symptoms associated with hypothyroidism may include:

• Difficulty concentrating or thinking
• Fatigue and tiredness
• Dry skin
• Hair loss, which may be in excess while showering
• Constipation or difficult bowel movements
• Weight gain that may be slow and gradual
• Heavy and irregular periods (in women)
• Abnormal sensitivity to cold; the affected individuals may not tolerate cold very well

How is Radiation-Induced Thyroiditis Diagnosed?

The diagnosis of Radiation-Induced Thyroiditis may involve the following tests and procedures:

• Checking complete medical history including occupation, medication, radiation exposure etc., followed by a physical examination
• Assessment of the signs and symptoms
• Blood tests to evaluate the levels of:
  • T3 and T4; thyroid hormones produced in the thyroid gland
  • Serum TSH
  • Antithyroid peroxidase antibody (anti-TPO); antibodies against thyroid peroxidase, an enzyme in the thyroid gland
  • Antithyroglobulin antibody; antibodies interacting with thyroglobulin, a protein found on the thyroid cells
  • Tests to diagnose any viral infections
• Ultrasound scans of the thyroid gland
• Fine needle aspiration (FNA) biopsy or core biopsy of the thyroid gland, if needed

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Radiation-Induced Thyroiditis?

Radiation-Induced Thyroiditis usually does not present any significant complications. However, in some cases, the complications may include:

• Emotional stress
• Thyrotoxicosis, or the presence of excess thyroid hormones in the body tissues
• Scarring and fibrosis of the thyroid gland that may result in irreversible damage; this may take place within 6 to 18 weeks
• Complications arising from any underlying disorder if present

How is Radiation-Induced Thyroiditis Treated?

The following treatment measures may be considered for Radiation-Induced Thyroiditis:

• Administration of pain relievers and steroids 
• Beta-blockers are known to relieve an elevated heart rate and excessive sweating, which are prescribed if needed
• Anti-thyroid drugs may be prescribed for hyperthyroidism, if necessary
• Sometimes, thyroid hormone replacement is needed if severe symptoms of hypothyroidism are noted 
• Follow-up care with screening and check-ups are important at regular intervals

How can Radiation-Induced Thyroiditis be Prevented?

Current medical research has not established a method of preventing Radiation-Induced Thyroiditis. However, the following measures may be considered to help lower one’s risk for the condition:

• Avail early treatment for any underlying conditions
• Periodic monitoring or follow-up of the condition with the healthcare provider is recommended

What is the Prognosis of Radiation-Induced Thyroiditis? (Outcomes/Resolutions)

The prognosis of Radiation-Induced Thyroiditis depends upon the extent of thyroid gland damage and resulting symptoms; the long-term prognosis is better, when thyroid dysfunction is not severely affected. In case of permanent damage causing low hormone levels, a lifelong use of medications may be needed.

Additional and Relevant Useful Information for Radiation-Induced Thyroiditis:

The following article links will help you understand thyroid-stimulating hormone (TSH), total T3, and total T4 laboratory tests:

http://www.dovemed.com/common-procedures/procedures-laboratory/thyroid-stimulating-hormone-tsh-test/

http://www.dovemed.com/common-procedures/procedures-laboratory/total-t3-blood-test/

http://www.dovemed.com/common-procedures/procedures-laboratory/total-t4-blood-test/