Conditions: Acute Thyroiditis

What is acute thyroiditis?

Acute thyroiditis (also called acute suppurative thyroiditis) is a condition characterized by the sudden development of inflammation and pain of the thyroid gland, usually in one subsite of the thyroid gland (most often the left lobe) rather than the entire gland. Bacterial infections are the usual cause of acute thyroiditis. In addition to pain, patients may also experience fever and a general feeling of being unwell. Although thyroid function is usually normal, in some cases acute thyroiditis can lead to the release of excessive thyroid hormones, resulting in temporary hyperthyroidism. Differentiating acute thyroiditis from a slower-onset subacute thyroiditis is important because acute thyroiditis is more likely to be bacterial and a subacute thyroiditis is more commonly viral. Treatment for bacterial acute thyroiditis usually involves antibiotics to address the underlying bacterial infection, along with pain relievers and anti-inflammatory medications to alleviate symptoms. Once the infection has resolved, individuals typically recover fully and regain normal thyroid function. In children and in people with repeated episodes, doctors will look for an underlying pyriform sinus fistula and correct it to prevent the infection from coming back.

What causes acute bacterial thyroiditis?

Common bacteria that can lead to acute bacterial thyroiditis include Staphylococcus aureus and Streptococcus species of bacteria. Infections can occur due to the spread of bacteria from nearby structures, such as the skin or throat, or through the bloodstream from distant sites. In children, a congenital pyriform sinus fistula — a small abnormal tract connecting the throat to the thyroid area, almost always on the left — is the most common source of infection. Other risk factors for acute bacterial thyroiditis include a compromised immune system, previous thyroid surgery or injury, and certain medical procedures or interventions that disrupt the normal defenses of the thyroid gland.

diagnosis

Diagnosis of acute bacterial thyroiditis begins with a history and physical exam, including identifying any recent infections or procedures in the neck area. Physical examination involving palpation of the thyroid gland may reveal signs of redness, warmth, tenderness and swelling. Laboratory tests such as a complete blood count (CBC) may be performed to assess for an elevated white blood count, specifically with elevated neutrophils, which would be supportive of a bacterial infection being present in the body. Inflammatory markers such as the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are also usually elevated. Occasionally, a A fine-needle aspiration biopsy (FNAB) is often the most useful test and is conducted to collect a sample of thyroid tissue for analysis, which is Gram-stained and cultured to confirm the presence of bacterial infection and to identify the specific bacteria so that antibiotics can be targeted. Imaging studies like ultrasound or CT scans of the neck are the imaging tests of choice and are also often utilized to visualize the thyroid gland*,* evaluate its size and structure*, and detect any abscess that may need drainage.*

It is important for a physician to differentiate the acute bacterial infection of acute bacterial thyroiditis from subacute granulomatous thyroiditis which is far more common. Subacute granulomatous thyroiditis is also painful, as is acute bacterial thyroiditis, but is characterized by a slower onset and protracted resolution than acute bacterial thyroiditis. In subacute granulomatous thyroiditis, the white blood cell count is usually normal or only mildly elevated — in contrast to the marked, neutrophil-predominant elevation typical of acute bacterial thyroiditis — while the ESR and CRP are markedly raised. A prompt, dramatic improvement with corticosteroids also points to subacute thyroiditis, whereas acute bacterial thyroiditis does not respond to steroids.

Treatment

The treatment approach for acute thyroiditis aims to resolve the infection and lessen pain. Because acute bacterial thyroiditis can be serious, affected individuals are often hospitalized and started on intravenous (IV) broad-spectrum antibiotics; these are then narrowed to target the specific bacteria once culture results are available. Common empiric choices include a penicillinase-resistant penicillin combined with a beta-lactamase inhibitor (such as piperacillin/tazobactam), with vancomycin added if a resistant organism (MRSA) is suspected. Nonsteroidal anti-inflammatory drugs (NSAIDs) may also be recommended to reduce pain and inflammation. If temporary hyperthyroidism causes symptoms such as a racing heartbeat, a beta-blocker may be used to control them. Surgical drainage may be necessary and accompanied by a search for a pyriform sinus fistula (part of a branchial cleft abnormality), particularly in children with thyroiditis involving the left lobe.