What Causes Thyroiditis? Understanding the Triggers and Risk Factors

Thyroiditis, a group of disorders characterized by inflammation of the thyroid gland, affects millions worldwide. While it manifests in various forms, the most common types seen in endocrinology include subacute thyroiditis, chronic lymphocytic thyroiditis (also known as Hashimoto's thyroiditis), and postpartum thyroiditis. Each type has distinct causes and underlying mechanisms, often involving immune system dysfunction, viral infections, or hormonal fluctuations. Understanding these triggers is essential for early diagnosis and effective management.

Subacute Thyroiditis: Linked to Viral Infections

Subacute thyroiditis is frequently associated with viral infections. Many patients report a recent upper respiratory tract infection—typically 1 to 3 weeks before symptoms appear. Common viruses implicated include coxsackievirus, mumps, and influenza. These infections can trigger an inflammatory response in the thyroid gland, leading to painful swelling in the neck, fever, fatigue, and general malaise.

The condition is believed to result from the immune system mistakenly attacking thyroid tissue following a viral illness. Unlike bacterial infections, antibiotics are ineffective; treatment usually focuses on relieving pain and managing inflammation with nonsteroidal anti-inflammatory drugs (NSAIDs) or, in severe cases, corticosteroids.

Chronic Lymphocytic Thyroiditis: A Blend of Genetics and Autoimmunity

Also known as Hashimoto's thyroiditis, this form is the most common cause of hypothyroidism in areas with sufficient iodine intake. It develops when the body's immune system launches a prolonged attack on the thyroid gland, gradually destroying its ability to produce hormones.

Key Contributing Factors Include:

Genetic predisposition: Individuals with a family history of autoimmune diseases—such as type 1 diabetes, lupus, or rheumatoid arthritis—are at higher risk. Specific genes related to immune regulation may increase susceptibility.

Immune system dysregulation: The presence of autoantibodies like anti-thyroid peroxidase (TPO) and anti-thyroglobulin antibodies confirms an autoimmune origin. Environmental factors such as stress, radiation exposure, or dietary components may act as catalysts in genetically prone individuals.

Postpartum Thyroiditis: Hormonal Shifts and Immune Rebound

This type occurs in 5% to 10% of women after childbirth and is considered an autoimmune condition that flares up during the postpartum period. During pregnancy, the immune system is naturally suppressed to protect the fetus. After delivery, there's a rebound effect where immune activity surges, sometimes targeting the thyroid gland.

Symptoms often appear in two phases: an initial hyperthyroid phase (due to hormone leakage from damaged cells), followed by a hypothyroid phase as the gland becomes exhausted. While some women recover fully, others may develop permanent hypothyroidism requiring lifelong thyroid hormone replacement.

Prevention and Management Strategies

Although not all cases of thyroiditis can be prevented, early detection through regular thyroid function tests—especially in high-risk groups—can improve outcomes. Maintaining a healthy lifestyle, managing stress, and monitoring for symptoms like unexplained weight changes, fatigue, or mood swings are practical steps toward better thyroid health.

For women with a history of autoimmune conditions or previous postpartum thyroid issues, discussing preventive screening with a healthcare provider during prenatal visits is highly recommended.