Thyroiditis is an inflammatory disease of the thyroid. It is a multifaceted disease with various etiologies, different clinical characteristics (depending on the stage), and distinct histopathology. Thyroiditis can be subdivided into three common types (Hashimoto, painful, and painless) and two rare forms (suppurative and Riedel). To add to the confusion, there are various synonyms for each form, and there is no internationally accepted classification of autoimmune thyroid disease.

Hashimoto thyroiditis: Chronic lymphocytic thyroiditis, chronic autoimmune thyroiditis, lymphadenoid goiter

Painful subacute thyroiditis: Subacute thyroiditis, giant cell thyroiditis, de Quervain thyroiditis, subacute granulomatous thyroiditis, pseudogranulomatous thyroiditis

Painless postpartum thyroiditis: Subacute lymphocytic thyroiditis, postpartum thyroiditis

Painless sporadic thyroiditis: Silent sporadic thyroiditis, subacute lymphocytic thyroiditis

Infectious thyroiditis: Acute suppurative thyroiditis, bacterial thyroiditis, microbial inflammatory thyroiditis, pyogenic thyroiditis

Riedel thyroiditis: Fibrous thyroiditis

• Thyroiditis typically has three phases: Thyrotoxic and hypothyroid (each lasting approximately 3 mo) and return to euthyroidism.
• Hashimoto: Patients may have signs of hyperthyroidism (tachycardia, diaphoresis, palpitations, weight loss) or hypothyroidism (fatigue, weight gain, delayed reflexes) depending on the stage of the disease. Usually there is diffuse, firm enlargement of the thyroid gland; the gland may also be of normal size (atrophic form with clinically manifested hypothyroidism).
• Painful subacute: Exquisitely tender, enlarged thyroid, fever; signs of hyperthyroidism are initially present; signs of hypothyroidism can subsequently develop.
• Painless thyroiditis: Clinical features are similar to subacute thyroiditis except for the absence of tenderness of the thyroid gland.
• Suppurative: Patient is febrile with severe neck pain, focal tenderness of the involved portion of the thyroid, erythema of the overlying skin.
• Riedel: Slowly enlarging hard mass in the anterior neck; often mistaken for thyroid cancer; signs of hypothyroidism occur in advanced stages.

• Hashimoto: Autoimmune disorder that begins with the activation of CD4 T-helper lymphocytes specific for thyroid antigens. The etiologic factor for the activation of these cells is unknown
• Painful subacute: Possibly postviral; usually follows a respiratory illness not considered to be a form of autoimmune thyroiditis
• Painless thyroiditis: Frequently occurs postpartum
• Infectious (suppurative): Infectious etiology, generally bacterial, although fungi and parasites have also been implicated; often occurs in immunocompromised hosts or after a penetrating neck injury
• Riedel: Fibrous infiltration of the thyroid; etiology unknown
• Drug induced: Typically painless due to lithium, interferon-alfa, amiodarone, interleukin-2
• Radiation thyroiditis: Occurs 5 to 10 days after treatment with radioactive iodine; it is painful and may result in transient exacerbation of hyperthyroidism

• The hyperthyroid phase of Hashimoto, subacute, and silent thyroiditis can be mistaken for Graves disease.
• Riedel thyroiditis can be mistaken for carcinoma of the thyroid.
• Painful subacute thyroiditis can be mistaken for infections of the oropharynx and trachea or for suppurative thyroiditis.
• Factitious hyperthyroidism can mimic silent sporadic thyroiditis.

• The diagnostic workup includes laboratory and x-ray evaluation to rule out other conditions that may mimic thyroiditis (see previously) and differentiate the various forms of thyroiditis.
• The patient’s medical history may be helpful in differentiating the various types of thyroiditis (e.g., presentation after childbirth is suggestive of silent [postpartum, painless] thyroiditis; occurrence after a viral respiratory infection suggests subacute thyroiditis; history of penetrating injury to the neck indicates suppurative thyroiditis).

• Thyroid-stimulating hormone, free T4: May be normal or indicative of hypothyroidism or hyperthyroidism depending on the stage of the thyroiditis.
• White blood cell (WBC) with differential: Increased WBC with left shift occurs with subacute and suppurative thyroiditis.
• Antimicrosomal antibodies: Detected in >90% of patients with Hashimoto thyroiditis and 50% to 80% of patients with silent thyroiditis.
• Serum thyroglobulin levels are elevated in patients with subacute and silent thyroiditis; this test is nonspecific but may be useful in monitoring the course of subacute thyroiditis and distinguishing silent thyroiditis from factitious hyperthyroidism (low or absent serum thyroglobulin level).

24-h radioactive iodine uptake (RAIU) is useful to distinguish Graves disease (increased RAIU) from thyroiditis (normal or low RAIU). Table E1 summarizes factors that influence 24-h thyroid iodide uptake.

• The duration of the thyrotoxic phase of thyroiditis is usually 10 to 12 wk. This phase is followed by a hypothyroid phase typically lasting up to 12 wk.
• Treat hypothyroid phase in symptomatic patients somatic with levothyroxine 25 to 50 mcg/day initially and monitor serum thyroid-stimulating hormone initially every 6 to 8 wk.
• Control symptoms of hyperthyroidism with β-blockers (e.g., propranolol 20 to 40 mg PO q6h or atenolol).
• Control pain in patients with subacute thyroiditis with NSAIDs. Prednisone 20 to 40 mg daily may be used if nonsteroidals are insufficient, but it should be gradually tapered off over several weeks.
• Use intravenous (IV) antibiotics and drain abscess (if present) in patients with suppurative thyroiditis.

• Hashimoto thyroiditis: Long-term prognosis is favorable; most patients recover their thyroid function.
• Painful subacute thyroiditis: Permanent hypothyroidism occurs in 10% of patients.
• Painless thyroiditis: 6% of patients have permanent hypothyroidism.
• Infectious thyroiditis: There is usually full recovery after treatment.
• Riedel thyroiditis: Hypothyroidism occurs when fibrous infiltration involves the entire thyroid.

• Surgical referral in patients with compression of adjacent neck structures and in some patients with infectious (suppurative) thyroiditis.
• Total thyroidectomy has been shown to improve symptoms in patients with Hashimoto thyroiditis who still have symptoms despite having normal thyroid gland function while receiving medical therapy.

Thyroiditis (Patient Information)

Hyperthyroidism (Related Key Topic)

Hypothyroidism (Related Key Topic)