Thyroiditis is a family of inflammatory thyroid disorders that share a transient or sustained disturbance of thyroid hormone release, with Hashimoto thyroiditis the dominant cause of hypothyroidism in iodine-replete countries — affecting roughly 5% of the US population over a lifetime. The classic triphasic pattern of painless and subacute thyroiditis runs from a thyrotoxic phase lasting 4-8 weeks, through a hypothyroid phase of 2-6 months, to recovery in 80% of cases.
Thyroiditis (ICD-10: E06) is a group of inflammatory conditions of the thyroid gland that share altered hormone release as their final common pathway. Five major forms exist. Hashimoto (chronic autoimmune lymphocytic) thyroiditis is mediated by T-cell infiltration of the gland and circulating antibodies to thyroid peroxidase (TPO) and thyroglobulin, producing progressive follicular destruction and permanent hypothyroidism. Subacute (de Quervain or granulomatous) thyroiditis is a post-viral inflammatory disorder producing painful gland destruction, transient thyrotoxicosis, and usually full recovery.
The key symptoms of Thyroiditis are: Painful, exquisitely tender thyroid gland with pain radiating to the ear or jaw in subacute thyroiditis — discomfort typically prevents the patient from buttoning a collar or turning the head., Painless diffuse goiter that develops gradually over months or years in Hashimoto thyroiditis, often firm and rubbery on palpation rather than tender., Symptoms of hyperthyroidism during the early thyrotoxic phase: palpitations, heat intolerance, tremor, weight loss despite increased appetite, anxiety, and loose stools., Symptoms of hypothyroidism in the subsequent phase or in established Hashimoto disease: fatigue, weight gain, cold intolerance, constipation, dry skin, hair thinning, and slowed cognition., Postpartum mood changes, anxiety, palpitations, and weight loss between 1-6 months after delivery in the thyrotoxic phase of postpartum thyroiditis., Persistent low-grade fever, malaise, and elevated inflammatory markers in subacute thyroiditis, often preceded by an upper respiratory infection 2-8 weeks earlier., Sudden onset of severe anterior neck pain, fever, fluctuant mass, and dysphagia in acute suppurative thyroiditis — a surgical emergency..
Diagnosis of thyroiditis combines clinical features, thyroid function tests, antibody screening, and selective imaging. TSH and free T4 establish whether the patient is currently hyperthyroid, euthyroid, or hypothyroid. TPO and thyroglobulin antibodies confirm autoimmune etiology — TPO antibodies are positive in 95% of Hashimoto disease and 60% of postpartum thyroiditis. Erythrocyte sedimentation rate above 50 mm/hour in a patient with painful neck swelling and thyrotoxicosis points to subacute thyroiditis; ESR is normal in painless and Hashimoto forms. The most decisive test for distinguishing thyroiditis from Graves disease in the thyrotoxic phase is radioactive iodine uptake (RAIU) — uptake is low (<5%) in thyroiditis because follicles are damaged and not synthesizing hormone, but high (>30%) in Graves disease. Thyroid ultrasound shows characteristic features: heterogeneous hypoechoic gland with diffusely increased vascularity (Hashimoto), focal hypoechoic regions with reduced vascularity (subacute), or stony-hard fibrosis with infiltrative pattern (Riedel). Fine-needle aspiration is reserved for atypical cases or suspected lymphoma — a known complication of long-standing Hashimoto disease. The differential includes Graves disease, factitious thyrotoxicosis, exogenous levothyroxine excess, struma ovarii, and metastatic thyroid carcinoma. In suspected suppurative thyroiditis, urgent neck CT and aspiration with culture confirm bacterial infection and guide drainage.
Prognosis varies by thyroiditis type. Subacute (de Quervain) thyroiditis resolves fully in 80-90% of cases over 4-6 months; 10-15% develop permanent hypothyroidism requiring lifelong replacement. Painless and postpartum thyroiditis follow the same triphasic pattern with 80% returning to euthyroid state; 20% become permanently hypothyroid and require replacement. Recurrence of postpartum thyroiditis occurs in 70% of subsequent pregnancies. Hashimoto disease is permanent — the autoimmune destruction does not reverse, but lifelong levothyroxine replacement fully controls symptoms in 95% of patients and provides normal life expectancy. Drug-induced thyroiditis usually resolves on stopping the offending agent; immune checkpoint inhibitor thyroiditis often leaves permanent hypothyroidism. Acute suppurative thyroiditis has over 90% cure rate with antibiotics and drainage but recurs without fistula correction. Riedel thyroiditis is rare and progressive but responds to immunomodulatory therapy. Long-standing Hashimoto disease modestly increases the risk of thyroid lymphoma (relative risk 60 versus general population, though absolute risk remains under 0.1% per year). The decisive prognostic factor across forms is timely recognition and appropriate management of each phase.
Endocrinologist referral is warranted for thyrotoxic-phase thyroiditis when the diagnosis is unclear, when there is uncertainty between thyroiditis and Graves disease, when subacute thyroiditis fails to respond to NSAIDs, when postpartum thyroiditis is recurrent across pregnancies, when checkpoint-inhibitor thyroiditis develops during cancer therapy, and when long-standing Hashimoto disease shows new nodules or rapid growth raising lymphoma concern.
Find specialists →Subacute thyroiditis pain resolves within 1-4 weeks of starting NSAIDs or corticosteroids. The triphasic course of painless, postpartum, and subacute thyroiditis runs over 4-6 months — thyrotoxic phase 4-8 weeks, hypothyroid phase 2-6 months, recovery in most patients. Drug-induced thyroiditis resolves within 1-3 months of discontinuing the offending agent. Hashimoto disease has no recovery — levothyroxine is started and continued for life; TSH targets are reached within 3-6 months of titration in most patients.
Regular aerobic and resistance exercise (150 minutes weekly of moderate activity plus 2 strength sessions) supports thyroid health, metabolic rate, and bone density. Defer strenuous training during the thyrotoxic phase of subacute or postpartum thyroiditis until symptoms settle. Cardiac assessment before resuming exercise is advisable in older patients with severe hyperthyroid symptoms.
Look for board certification in endocrinology, experience with autoimmune thyroid disease, comfort with the RAIU vs Graves distinction in the thyrotoxic phase, and familiarity with checkpoint-inhibitor endocrinopathies if you are on cancer immunotherapy. For suppurative thyroiditis, ENT or head-and-neck surgical input is essential. Continuity matters: long-term levothyroxine titration is a multi-year relationship.
Medically reviewed by AIHealz Medical Editorial Board · May 13, 2026
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