What Is Subacute Thyroiditis?

Subacute thyroiditis is a relatively common clinical type of thyroid disease, predominantly affecting middle-aged and young women. It often develops following a recent viral infection in the patient. So, what exactly is subacute thyroiditis? The following section addresses this question.

Subacute thyroiditis is also known as subacute granulomatous thyroiditis, giant cell thyroiditis, noninfectious thyroiditis, transient thyroiditis, viral thyroiditis, granulomatous thyroiditis, or giant cell thyroiditis. In recent years, its incidence has gradually increased. Its clinical presentation is complex and variable, leading to frequent misdiagnosis or missed diagnosis, and it tends to recur—thereby compromising overall health. Nevertheless, most patients achieve full recovery. This condition exhibits epidemic characteristics, with clustering of cases observed during certain seasons or viral outbreaks. Although mumps virus has been isolated from thyroid tissue of some subacute thyroiditis patients, definitive evidence confirming a viral etiology remains lacking.

Knowledge Expansion: Clinical Manifestations of Subacute Thyroiditis

1. Early Phase

Onset is typically abrupt, characterized by fever accompanied by chills, fatigue, malaise, and anorexia. The most characteristic feature is pain and tenderness localized to the thyroid region, often radiating to the submandibular area, ears, or neck. Pain intensifies during chewing or swallowing. Thyroid involvement may be unilateral initially, subsequently spreading to or involving the contralateral lobe.

2. Intermediate Phase

As thyroid follicular cells are damaged by inflammation, stored thyroid hormone is depleted. Before thyroid parenchymal cells regenerate, serum thyroid hormone levels may decline to hypothyroid levels, clinically manifesting as hypothyroidism. Meanwhile, systemic symptoms become milder, and patients may exhibit neither hyperthyroid nor hypothyroid features.

3. Recovery Phase

Symptoms gradually improve; thyroid enlargement and/or nodules resolve progressively. In many cases, small residual nodules persist but slowly regress over time. With timely treatment, most patients recover completely; permanent hypothyroidism is exceedingly rare. In mild or atypical cases, only slight thyroid enlargement occurs, with minimal pain and tenderness and absence of fever.

The above provides an overview of subacute thyroiditis. We hope this information proves helpful to you.