Riedel Thyroiditis - Symptoms, Diagnosis, and Treatment

Introduction:

Riedel thyroiditis is a rare fibrotic condition affecting the thyroid gland, which often involves surrounding tissues and structures of the gland. Due to the rarity of the condition, the exact incidence of the disease is unknown. However, it is more common in females than males, and the average age of onset is around 48 years. Some patients affected by the condition remain euthyroid (normally functioning thyroid), while most patients show symptoms of hypothyroidism (underactive thyroid), and very few patients develop hyperthyroidism (overactive thyroid). The main symptoms of the condition are due to compression of the food pipe or windpipe by the thyroid mass.

What Is Thyroiditis?

The thyroid gland is a small butterfly-shaped gland in front of the neck responsible for synthesizing and secretion of thyroid hormones. Thyroiditis can be defined as the swelling or inflammation of the thyroid gland that can result in an overactive (hyperthyroidism) or an underactive thyroid gland (hypothyroidism). Thyroiditis can occur due to the autoimmune response of the body (some people develop anti-thyroid antibodies), primary fibrotic disorder, viral infections, and side effects of drugs. The clinical course of thyroiditis depends upon the type of thyroiditis. However, there are three phases of thyroiditis:

1. Thyrotoxic Phase: In this phase, the thyroid glands become swollen and release too much thyroid hormone.

2. Hypothyroid Phase: During this phase, following the oversecretion of thyroid hormone in the thyrotoxic phase for a few weeks, the thyroid gland will not have any more thyroid hormone left to release. Therefore, this will lead to a phase of hypothyroidism.

3. Euthyroid Phase: This phase may come temporarily before the hypothyroid phase. But mostly, this phase comes after the thyroid gland has recovered from inflammation and the gland can maintain a normal level of thyroid hormones.

What Is Riedel Thyroiditis?

Riedel thyroiditis is a rare and inflammatory condition affecting the thyroid gland, characterized by fibrosis of the thyroid gland and surrounding tissues. The condition is associated with several types of systemic fibrosis. Moreover, fibrosis is the process of scarring and thickening of tissues to form fibrous tissues, which occurs when collagen production by fibroblasts exceeds the rate of its degradation. It is associated with hypothyroidism (underactive thyroid gland) and is clinically present as a “stone-like” fibrous condition of the thyroid gland. In the case of Riedel’s thyroiditis, the thyroid gland becomes non-tender and hard as wood. During the disease, the tissues surrounding the thyroid gland are also replaced by thick fibrous tissues. The invasion of fibrosis in the surrounding tissues may include the parathyroid gland, muscles, blood vessels, nerves, and sometimes the windpipe (trachea).

What Are the Other Names of Riedel Thyroiditis?

Other names of Riedel thyroiditis are:

• Riedel struma.

• Chronic invasive fibrous thyroiditis.

• Ligneous struma.

What Causes Riedel Thyroiditis?

• The exact cause of Riedel thyroiditis is unknown. However, some theories suggest it could be a variation of autoimmune thyroiditis or Hashimoto’s thyroiditis.

• Another theory suggests that it may be a part of systemic fibrosis disorder.

• It is also speculated that Riedel thyroiditis is associated with the autoimmune response of the body in which there is stimulation of fibrosis in the affected tissues. This theory has been supported by certain clinical and lab findings like anti-thyroid antibodies, cellular infiltration, and the fact that the condition responds well to systemic corticosteroids.

How Common Is Riedel Thyroiditis?

• Riedel thyroiditis is a rare condition affecting the thyroid gland. It is the least prevalent of all the conditions causing thyroiditis.

• The estimated rate of occurrence is 0.16 cases per 1,00,000 population.

• The condition is more common in females as compared to males. And the average onset is between 30 to 50 years.

What Are the Symptoms of Riedel Thyroiditis?

The symptoms of Riedel thyroiditis are similar to that of anaplastic thyroid carcinoma (highly aggressive cancerous thyroid gland tumors). The symptoms include:

• Hard and woody thyroid gland on palpation.

• Immobile thyroid mass.

• Rapidly growing thyroid mass.

• Painless thyroid mass.

• Tightness of the neck.

• The feeling of pressure on the neck.

• Hoarseness of the voice.

• Difficulty in swallowing (dysphagia) due to involvement of the food pipe.

• Difficulty in breathing (dyspnea) due to the involvement of the windpipe.

• Cough.

• Choking may occur due to extreme compression of the trachea by the fibrotic thyroid mass.

• Presence of whistling sound while breathing (stridor) due to the involvement of the laryngeal nerve.

• Bulging of eyes due to involvement of retrobulbar tissues.

How Is Riedel Thyroiditis Diagnosed?

The diagnosis of Riedel thyroiditis is made in the following ways:

• Blood Examination: During blood examinations, several tests are done, including a thyroid function test to measure the levels of thyroid-stimulating hormone, thyroxine (T4), triiodothyronine (T3), etc. In the case of Riedel thyroiditis, a thyroid function test reveals hypothyroidism (overactive thyroid) in about 74 % of the people. Thyroid antibodies are also positive in the case of Riedel thyroiditis.

• Erythrocyte Sedimentation Rates (ESR): These are elevated in the case of Riedel thyroiditis.

• Imaging Tests: Ultrasonography of the neck will show a fibrotic hypovascular thyroid mass that may also involve the surrounding tissues. CT scans (computed tomography) and MRI (magnetic resonance imaging) are done further to study the nature of the mass in detail. During a CT scan, the mass will appear as hypodense that does not enhance with contrast.

• Nuclear Scan: Nuclear scanning will show a cold uptake area at the site of affected tissues.

• Definitive Diagnosis: A definitive diagnosis of Riedel thyroiditis is made based on the following criteria; involvement of tissues and structures outside the thyroid gland, presence of occlusive inflammation of veins, absence of granulomas, giant cells, etc., in laboratory findings, and absence of any kind of cancerous lesion.

How Is Riedel Thyroiditis Treated?

There are no standardized treatment modalities for Riedel thyroiditis due to the condition's rarity. However, the following treatments are being used presently to treat patients with Riedel thyroiditis:

• Thyroidectomy: Partial or complete surgical removal of the thyroid gland is the treatment of choice in case of extensive involvement of the surrounding tissues that may lead to compressive symptoms like dysphagia and dyspnea. However, the risk of developing complications after surgery is high in the case of Riedel thyroiditis (about 39 %). Therefore, less invasive surgical inventions like wedge resection of the isthmus of the thyroid may be done.

• Medications: The use of glucocorticoids is the cornerstone of medical treatment. During the early stages of the condition, the anti-inflammatory effects of glucocorticoids are exceptionally beneficial. A dosage of 15 mg (milligrams) to 100 mg of Prednisone may be advised depending on the severity of the condition. Tamoxifen is a drug classified as a selective estrogen receptor modulator, and it induces tumor growth factor-beta which is effective in inhibiting growth. A dosage of 10 mg to 20 mg (given alone or in combination with Prednisone) is useful in treating Riedel thyroiditis.

Conclusion:

Riedel thyroiditis is usually a self-limiting condition with an excellent prognosis. It is not a life-threatening condition unless left untreated, the compressive symptoms become very severe, and complete obstruction of the trachea (windpipe) occurs, leading to choking. Surgery for patients with Riedel thyroiditis serves two purposes; it establishes the diagnosis and relieves the patient from the compression of the windpipe. A wedge resection of the isthmus of the thyroid gland is the preferred method of noninvasive surgical intervention for the condition.