Silent Thyroiditis - Causes, Symptoms, Diagnosis, and Treatment

Introduction:

Silent thyroiditis is the inflammation of the thyroid gland occurring due to unknown reasons. The body’s immune response starts producing antithyroid antibodies, which attack the healthy thyroid cells. The clinical course of silent thyroiditis starts with hyperthyroidism (overactive thyroid), then the euthyroid phase (normally functioning thyroid), followed by hypothyroidism (underactive thyroid), and then again the euthyroid phase. Like any other thyroid disease, silent thyroiditis is more common in women. However, the exact rate of incidence of the disease in the general population is unknown.

What Is the Thyroid Gland?

The thyroid, or the thyroid gland, is a small, vascular, and butterfly-shaped endocrine gland located in front of the neck below the laryngeal prominence. The thyroid gland consists of two lobes connected in their lower one-third part through a band of tissues called the thyroid isthmus. The thyroid gland is responsible for the production and secretion of the thyroid hormones; thyroxine (T4), triiodothyronine (T3), and calcitonin. These hormones are crucial for growth, development, metabolism, protein synthesis, maintaining calcium balance in the body, etc. Any imbalance in the levels of thyroid hormones can lead to the development of several thyroid disorders like; hypothyroidism (decreased production of thyroid hormones), hyperthyroidism (increased production of thyroid hormones), thyroiditis (inflammation of the thyroid), goiter (formation of a lump in the thyroid), thyroid nodules, thyroid cancer, etc.

What Is Thyroiditis?

Thyroiditis is a thyroid gland disorder characterized by swelling or inflammation of the gland. This can result in hyperthyroidism (overactive thyroid leading to excess thyroid hormone production) or hypothyroidism (underactive thyroid leading to lack of thyroid hormones). Thyroiditis can be caused by the body's autoimmune reaction (some patients generate anti-thyroid antibodies), viral infections, medication side effects, etc. The clinical course of thyroiditis is determined by its type. However, there are three phases of thyroiditis:

• Thyrotoxic Phase: During the thyrotoxic phase, the thyroid gland becomes swollen and starts producing and secreting excess thyroid hormones.

• Hypothyroid Phase: After a few weeks of over-secretion of the thyroid hormones, the thyroid gland is left with no more thyroid hormones to release. This leads to a lack of thyroid hormone and hypothyroidism or hypothyroid phase.

• Euthyroid Phase: This phase may appear transient before the hypothyroid phase. But more commonly, this phase starts after the swelling and inflammation of the thyroid gland subside, and the gland regains its normal functioning. A normal thyroid level is maintained in this phase.

What Are the Different Types of Thyroiditis?

The various types of thyroiditis classified based on their cause are:

• Silent Thyroiditis: It is an autoimmune condition that occurs due to the presence of antithyroid antibodies in the body.

• Subacute Thyroiditis: It is a type of thyroiditis occurring due to viral infections.

• Hashimoto’s Thyroiditis: This is also an autoimmune condition leading to inflammation of the thyroid gland.

• Postpartum Thyroiditis: Thyroid inflammation after childbirth is known as postpartum thyroiditis. Postpartum thyroiditis can cause hyperthyroidism followed by hypothyroidism. An autoimmune condition comparable to Hashimoto's thyroiditis is suspected of causing postpartum thyroiditis.

• Drug-induced Thyroiditis: This is a type of thyroid gland inflammation occurring due to the side-effect of certain drugs like Amiodarone, Lithium, Interferon, cytokines, etc.

• Radiation-induced Thyroiditis: Thyroiditis occurs due to radiation exposure or following treatment with radioactive iodine.

• Acute Thyroiditis: Inflammation of the thyroid gland occurs due to bacterial infection or infection from any other infectious organism.

What Is Silent Thyroiditis?

• Silent thyroiditis is a type of thyroiditis occurring due to an immune reaction of the thyroid gland. An autoimmune response is a condition in which the immune system of the body starts attacking the healthy cells of the body. There is the presence of anti-thyroid antibodies in the case of silent thyroiditis.

• Silent thyroiditis, along with post-partum thyroiditis, can be considered a variant of Hashimoto’s thyroiditis because, in all of these cases, antithyroid antibodies are present.

• During silent thyroiditis, the patient may develop a small lump in the gland without tenderness.

• Silent thyroiditis usually involves a period of hyperthyroidism followed by a euthyroid phase (normal functioning of the thyroid gland), then a period of hypothyroidism followed by a return to the euthyroid phase. The duration of each phase varies, but it normally lasts two to three months.

• Silent thyroiditis is painless and more prevalent among women as compared to men.

What Are the Other Names of Silent Thyroiditis?

Alternative names for silent thyroiditis are:

• Lymphocytic thyroiditis.

• Subacute lymphocytic thyroiditis.

• Painless thyroiditis.

• Thyroiditis-silent.

• Hyperthyroidism-silent thyroiditis.

What Causes Silent Thyroiditis?

The primary cause of silent thyroiditis is the autoimmune response of the body, which leads to the formation of anti-thyroid antibodies that attacks healthy thyroid cells. The reason why the body starts attacking its healthy cells is unknown. A variant of silent thyroiditis can occur in women after childbirth called postpartum thyroiditis. Certain medicines, like Interferon, Amiodarone, etc., can cause silent thyroiditis in rare cases. Certain radioactive therapy and chemotherapies may also cause thyroiditis.

What Are the Symptoms of Silent Thyroiditis?

Symptoms of silent thyroiditis are usually mild, and the euthyroid phase has no symptoms because the thyroid functioning is normal.

The symptoms during the hyperthyroid phase are:

• Fatigue.

• Irritability and restlessness.

• Anxiety.

• Heat intolerance.

• Increased bowel movement.

• Hair loss.

• Altered mood.

• Tremors.

• Excessive sweating.

• Unusual weight loss (with normal appetite).

• Palpitations and rapid heartbeat.

• Irregular menstrual cycles in women.

The symptoms during the hypothyroid phase are:

• Fatigue.

• Intolerance towards cold.

• Unusual weight gain.

• Depression.

• Irregular and heavy menstrual cycles.

• Constipation.

• Mood changes.

• Dryness of skin.

How Is Silent Thyroiditis Diagnosed?

The diagnosis of silent thyroiditis is made with the help of the following tests and examinations:

• A detailed medical and family history should be taken along with a thorough physical and clinical examination of the patient.

• Radioactive Iodine Uptake Test: A radioactive iodine uptake test can accurately detect silent thyroiditis. Radioiodine uptake is reduced during both the hyperthyroid and hypothyroid phases. The amount of radioactive iodine taken up by the thyroid gland during this test is measured. A pill containing a small amount of radioactive iodine is given to the patient during a radioactive iodine uptake test. After taking the pill, the patient is instructed to wait for the iodine to collect in the thyroid. The first uptake is done four to six hours after taking the iodine pill. A scan will show localized radioactive iodine uptake by the thyroid tissues.

• Blood Tests: Blood examinations are done to check the levels of thyroxine, triiodothyronine, thyroid-stimulating hormone, and C-reactive proteins in the body.

• Erythrocyte sedimentation rate (ESR) is done to determine any type of inflammatory activity in the body.

How Is Silent Thyroiditis Treated?

The treatment modalities for the management of silent thyroiditis include:

• Silent thyroiditis is usually a self-limiting condition, which means the condition subsides after some time without any treatment.

• In case of moderate to severe symptoms, medications and therapies are given to provide symptomatic relief.

• Beta-blockers are also advised to reduce blood pressure which causes palpitation in the early stages of silent thyroiditis (palpitations and high blood pressure occur due to thyrotoxicosis).

• Thyroid hormone replacement therapy is given to patients during the hypothyroid phase.

Conclusion:

Silent thyroiditis is a painless thyroid gland inflammation, often presenting with either no symptoms or very mild symptoms. However, in case of exaggerated symptoms, the condition requires symptomatic treatment. The prognosis of silent thyroiditis is excellent; within a year, it usually goes away on its own. Within three months, the acute phase ends. Hypothyroidism is a condition that affects some people over time. They must be treated with a drug that replaces thyroid hormones. However, in most cases, the patient regains normal thyroid functioning.