Know Thyroid Antibodies

Thyroiditis is a general term that refers to “inflammation of the thyroid gland”.

Thyroiditis includes a group of individual disorders causing thyroidal inflammation but presenting in different ways.

Thyroiditis is caused by an attack on the thyroid, causing inflammation and damage to the thyroid cells. Antibodies that attack the thyroid cause most types of thyroiditis. As such, thyroiditis is often an autoimmune disease, like juvenile (type 1) diabetes and rheumatoid arthritis. It is not known why certain people make anti-thyroid antibodies, although this tends to run in families. Thyroiditis can also be caused by an infection, such as a virus or bacteria, which can also cause inflammation in the gland. Finally, drugs such as interferon and amiodarone, can also damage thyroid cells and cause thyroiditis.

Who are more at risk of developing thyroiditis:

Being a woman. Women are about 7 times more likely to have the disease. Hashimoto's thyroiditis sometimes begins during pregnancy.

Middle age. Most cases happen between 40 to 60 years of age. But it has been seen in younger people.

Heredity. The disease tends to run in families. But no gene has been found that carries it.

Autoimmune diseases. These health problems raise a person’s risk. Some examples are rheumatoid arthritis and type 1 diabetes. Having this type of thyroiditis puts you at higher risk for other autoimmune illnesses.​

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THERE ARE MANY TYPES OF THYROIDITIS, WHICH ARE SUMMARIZED IN THE TABLE BELOW:

TYPE	CAUSE	CLINICAL FEATURES	DIAGNOSIS (not all tests may be needed)	DURATION AND RESOLUTION
Hashimoto’s thyroidits	Anti-thyroid antibodies, autoimmune disease	Hypothyroidism, rare cases of transient thyrotoxicosis	Thyroid function tests, thyroid antibody tests	Hypothyroidism is usually permanent
Subacute thyroiditis (de Quervain’s thyroiditis)	Possible viral cause	Painful thyroid, thyrotoxicosis followed by hypothyroidism	Thyroid function tests, sedimentation rate, radioactive iodine uptake	Resolves to normal thyroid function within 12-18 months, 5% possibility of permanent hypothyroidism.
Silent thyroiditis, Painless thyroiditis	Anti-thyroid antibodies, autoimmune disease	Thyrotoxicosis followed by hypothyroidism.	Thyroid function tests, thyroid antibody tests, radioactive iodine uptake	Resolves to normal thyroid function within 12-18 months, 20% possibility of permanent hypothyroidism.
Post partum thyroiditis	Anti-thyroid antibodies, autoimmune disease	Thyrotoxicosis followed by hypothyroidism.	Thyroid function tests, thyroid antibody tests, radioactive iodine uptake (contraindicated   if the hypothyroid woman is breast-feeding)	Resolves to normal thyroid function within 12-18 months, 20% possibility of permanent hypothyroidism
Drug induced	Drugs include: amiodarone, lithium, interferons, cytokines	Either thyrotoxicosis or hypothyroidism.	Thyroid function tests, thyroid antibody tests	Often continues as long as the drug is taken
Radiation induced	Follows treatment with radioactive iodine for hyperthyroidism or external beam radiation therapy for certain cancers.	Occasionally thyrotoxicosis, more frequently hypothyroidism..	Thyroid function tests	Thyrotoxicosis is transient, hypothyroidism is usually permanent
Acute thyroiditis, Suppurative thyroiditis	Bacteria mainly, but any infectious organism	Occasionally painful thyroid, generalized illness, occasional mild hypothyroidism	Thyroid function tests, radioactive iodine uptake, fine needle aspiration biopsy	Resolves after treatment of infectious cause, may cause severe illness​

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Clinical Manifestations of Thyroiditis Subtypes

SUBTYPE	ETIOLOGY	NECK PAIN	RAIU	TSH	T4	THYROID AUTOANTIBODIES
Chronic lymphocytic (Hashimoto's disease)	Autoimmune	No	Variable	Variable	Variable	Present
Subacute granulomatous	Viral	Yes	Decreased	Decreased	Increased	Absent
Subacute lymphocytic	Autoimmune	No	Decreased	Decreased	Increased	Present
Microbial inflammatory	Bacterial, fungal, parasitic	Yes	Variable	Normal	Normal	Absent
Hashitoxicosis	Autoimmune	No	Decreased	Decreased	Increased	Present
Invasive fibrous	Unknown	No	Variable	Normal	Normal	Variable​

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RAIU = radioactive iodine uptake; TSH = thyroid-stimulating hormone; T4 = thyroxine.

 

Antibodies mistakenly target the body’s own tissues. These antibodies that attack the patient’s own body are also known as autoantibodies or antithyroid antibodies. Thyroid antibody testing may look for several types of thyroid antibodies, the two most common being:

• Thyroid peroxidase antibodies (TPOAb): Thyroid peroxidase is an enzyme that is crucial to the production of thyroid hormones. TPOAb may interfere with the action of this enzyme. Almost all patients with Hashimoto’s thyroiditis have high levels of TPOAb.
• Thyroglobulin antibodies (TgAb): Thyroglobulin is a protein made by the thyroid gland. TgAb may be present when the thyroid has been damaged. Thyroglobulin antibodies are often measured in addition to thyroglobulintests after a patient completes treatment for thyroid cancer.​

Agilus Diagnostics, a subsidiary of Fortis Healthcare Limited