What Causes Thyroiditis?

Medically reviewed by Ana Maria Kausel, MD

"Thyroiditis" means inflammation of the thyroid gland. There are several different types of thyroiditis, depending on what is causing the gland to be inflamed in the first place, like an infection versus an autoimmune process.

Symptoms of thyroiditis, either those of an underactive thyroid gland (hypothyroidism) or an overactive thyroid gland (hyperthyroidism), tend to occur in phases. A clinical examination, in addition to blood and imaging tests, is needed to diagnose thyroiditis. Treatment is based on the thyroiditis type and the symptoms a patient is experiencing.

This article will discuss the different types of thyroiditis along with their causes. It also addresses the symptoms, diagnosis, and treatments of thyroiditis.

Takeaway

The thyroid gland is a small, butterfly-shaped gland located in your neck. It produces two thyroid hormones—thyroxine (T4) and triiodothyronine (T3). The function of these hormones is to regulate your body's metabolism and temperature.

What Are the Types and Causes of Thyroiditis?

The types of thyroiditis can be categorized by their underlying etiology (cause or origin).

Hashimoto's Thyroiditis

Hashimoto's thyroiditis, also called Hashimoto's disease, occurs when a person's own immune system attacks the thyroid gland, leading to its eventual destruction. This lifelong autoimmune disease causes permanent hypothyroidism.

Hashimoto's disease is more common in people born female, especially those between the ages of 30 and 50 years, and in individuals with other autoimmune diseases (e.g., type 1 diabetes or rheumatoid arthritis).

Related: Hashimoto’s Disease

Subacute (de Quervain's) Thyroiditis

Subacute thyroiditis is believed to be triggered by a viral infection. It occurs in two phases—a hyperthyroid phase and a hypothyroid phase, followed by recovery. The hyperthyroid phase causes a patient's thyroid gland to be tender to touch and abnormally enlarged (called a goiter).

Like Hashimoto's thyroiditis, this type of thyroiditis is more common in women, especially those in their thirties to fifties.

Postpartum Thyroiditis

Postpartum thyroiditis occurs when the thyroid gland becomes inflamed after a person has a baby, miscarriage, or abortion. It occurs within a year of a person being pregnant and causes temporary hyperthyroidism, hypothyroidism, or both (one phase following the other).

Approximately 3–8% of postpartum people in the general population are affected by this disorder, and the incidence is even higher in those with other autoimmune diseases. About 1 in 5 people who experience postpartum thyroiditis go on to have permanent thyroid issues.

Related: Postpartum Thyroiditis and Related Issues After Pregnancy

Silent (Painless) Thyroiditis

Silent thyroiditis, also called painless thyroiditis, causes a mild, short-lived hyperthyroid phase that is sometimes followed by a hypothyroid phase, and then recovery. With this type of thyroiditis, the thyroid gland remains normal in size or becomes mildly enlarged, but the patient doesn't experience any neck pain.

Silent thyroiditis accounts for up to 5% of cases of hyperthyroidism and is often autoimmune-mediated (meaning the culprit behind the inflammation is an immune system attack).

Drug-Induced Thyroiditis

Certain drugs can trigger thyroid gland inflammation (most commonly, painless thyroiditis) with variable effects on thyroid function. These drugs include:

• Interferon-alpha: This medication is used to treat certain cancers, like malignant melanoma, and certain viral infections, like chronic hepatitis C.

• Amiodarone: This drug is used to treat patients with various types of heart arrhythmias.

• Lithium: This drug is used to treat bipolar disorder and sometimes (off-label) unipolar depression.

• Tyrosine kinase inhibitors: These targeted drugs are used to treat different cancers, such as renal cell carcinoma and medullary thyroid cancer.

• Checkpoint inhibitor drugs: These drugs, such as Yervoy (Ipilimumab) and Tecentriq (Atezolizumab), work by boosting a patient's immune system response against cancer cells.

Radiation Thyroiditis

Radiation thyroiditis may develop within days of a patient being treated with radioiodine therapy for Graves' disease (an autoimmune disease that causes hyperthyroidism). This type of thyroiditis may cause mild neck discomfort and sometimes, a temporary worsening of hyperthyroid symptoms.

Acute Infectious Thyroiditis

Acute infectious thyroiditis occurs when virtually any bacteria, such as Staphylococcus ("Staph") or Streptococcus ("Strep"), infects the thyroid gland. While overall a rarer form of thyroiditis, it is more common in children.

The infection may result from a bloodstream infection, deep neck infection, or after a diagnostic fine-needle aspiration (FNA) of a thyroid nodule. In children, the infection usually stems from an internal fistula from the pyriform sinus (a pear-shaped depression located on either side of the larynx, which houses your vocal cords).

People with acute infectious thyroiditis may experience the sudden onset of one-sided neck pain, fever, chills, and the presence of a warm, red, and tender neck mass. Swallowing is painful. Thyroid function usually remains normal, although, hyperthyroidism or hypothyroidism may occur.

Related: What to Know About Acute Infectious Thyroiditis

Chronic Infectious Thyroiditis

Chronic infectious thyroiditis is usually caused by a fungus and tends to occur in patients with a weakened immune system. Thyroid gland tenderness is milder than in acute infectious thyroiditis and occurs on both sides. Some patients with this type of thyroiditis develop hypothyroidism.

How Does Thyroiditis Make You Feel?

The symptoms of thyroiditis depend on how quickly the thyroid cells are damaged and destroyed by the underlying inflammation.

If the thyroid cells are slowly destroyed, as in Hashimoto's thyroiditis, thyroid hormone levels will decrease gradually over time. This leads to symptoms of hypothyroidism, such as:

• Fatigue and exhaustion

• Mild weight gain

• Dry skin

• Decreased sweating

• Constipation

• Intolerance to cold

If the thyroiditis causes the thyroid cells to be rapidly destroyed, the thyroid hormones will quickly leak out of the gland and into the patient's bloodstream. This process is called thyrotoxicosis, and it causes symptoms of hyperthyroidism, such as:

• Increased sweating and heat intolerance

• Anxiety and insomnia

• Weight loss, even when eating normally

• Fast heart rate

• Frequent bowel movements

• Fatigue or weakness

How Thyroiditis Is Diagnosed

The diagnosis of thyroiditis includes a clinical examination, blood tests, and various imaging tests.

Clinical Examination

In addition to carefully reviewing your symptoms, your healthcare provider will inquire about your past medical history, like a prior pregnancy, viral infection, or history of autoimmune disease. A review of your medications and family history of thyroid disease, as well as a focused exam of your thyroid gland, will be performed.

Blood Tests

Thyroid function tests, which include a measure of thyroid-stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3), will be ordered. Thyroid antibodies to diagnose Hashimoto's thyroiditis (called anti-thyroid peroxidase antibodies) may also be ordered. Erythrocyte sedimentation rate (ESR) will be ordered if subacute thyroiditis is suspected.

Imaging

Imaging tests—a radioactive iodine uptake (RAIU) test and a thyroid ultrasound—may be performed to confirm the diagnosis of certain types of thyroiditis and to rule out any alternative diagnosis (e.g., Graves' disease).

What Is the Treatment for Thyroiditis?

Treatment of thyroiditis depends on the type of thyroiditis and the symptoms present. Some of the common medications used include:

• Beta blockers: A beta blocker can help ease hyperthyroid symptoms like a fast heart rate or anxiety.

• Anti-inflammatory drugs: Nonsteroidal anti-inflammatory drugs (NSAIDs) and less commonly, a corticosteroid (e.g., prednisone), can ease pain and swelling associated with thyroiditis

• Thyroid hormone replacement: Levothyroxine, the synthetic form of T4, is used to treat symptomatic hypothyroidism from subacute, painless, and post-partum thyroiditis. Since the hypothyroid phase is usually temporary in these conditions, therapy is typically only indicated for about six to 12 months. Hashimoto's thyroiditis is a chronic condition and therefore, requires lifelong treatment with levothyroxine.

• Antithyroid medications: Antithyroid medications are not generally indicated in the hyperthyroid phase of thyroiditis—one rare exception is in the treatment of some cases of amiodarone-induced thyroiditis.

Related: How to Take Your Thyroid Medication

Summary

Thyroiditis is an umbrella term for a number of disorders that cause thyroid inflammation but are nevertheless unique in their symptoms and etiology. Thyroiditis may occur because of an autoimmune process, infection, medication, or pregnancy.

Depending on the type of thyroiditis you have, you may experience symptoms of hypothyroidism (e.g. exhaustion, decreased sweating, intolerance to cold) or hyperthyroidism (e.g. anxiety, increased sweating, frequent bowel movements). The medications prescribed also depend on the type of thyroiditis and include beta blockers for some hyperthyroidism symptoms, anti-inflammatory drugs, levothyroxine (thyroid hormone replacement), and antithyroid medications.

If you have been diagnosed with thyroiditis, talk with your healthcare provider about the expected outcome of your condition. For Hashimoto's thyroiditis, hypothyroidism is permanent, whereas, for most other types, the changes in thyroid function are temporary (although, they can last up to 18 months).

Read the original article on Verywell Health.