Can the hyperthyroidism phase present with prolonged fever, such as fever lasting 20 days?

Can Hyperthyroidism Present as Prolonged Fever for 20 Days?

Hyperthyroidism itself does not typically cause prolonged fever lasting 20 days, but fever can occur in two specific contexts: thyroid storm (a life-threatening emergency) or concurrent thyroiditis, and you must urgently evaluate for these conditions while excluding other infectious or inflammatory causes.

When Fever Occurs with Hyperthyroidism

Thyroid Storm

• Fever is a cardinal feature of thyroid storm, an extreme hypermetabolic state that represents a medical emergency with approximately 90% mortality if undiagnosed 1, 2
• Thyroid storm presents with fever, tachycardia out of proportion to the fever, altered mental status (nervousness, restlessness, confusion, seizures), vomiting, diarrhea, and cardiac arrhythmia 1
• An inciting event (surgery, infection, labor, delivery) is typically identified as a trigger 1
• However, thyroid storm is an acute crisis, not a chronic condition lasting 20 days—if fever persists this long, you must consider alternative diagnoses 2

Subacute Thyroiditis with Hyperthyroid Phase

• Subacute thyroiditis can present with fever, neck pain, and a tender thyroid gland during its initial hyperthyroid phase 3, 4
• One case report documented a patient who developed "painful tender thyroid enlargement with a fever and accelerated erythrocyte sedimentation rate" during hyperthyroidism treatment 3
• The hyperthyroid phase of thyroiditis is self-limiting and typically lasts 2-8 weeks, during which fever may be present 1
• Patients may benefit from beta blockers (atenolol 25-50 mg daily) if symptomatic during this phase 1

Critical Differential Diagnoses to Exclude

Concurrent Infections

• You must actively search for infectious causes when a hyperthyroid patient presents with prolonged fever, as hyperthyroidism does not explain 20 days of fever 5
• One documented case showed a patient with Graves' disease and prolonged fever (>1 month) who was ultimately diagnosed with melioidosis, a bacterial infection 5
• Consider that hyperthyroid patients may have impaired immune responses or concurrent conditions that predispose to infection 5

Drug-Induced Fever from Antithyroid Medications

• Agranulocytosis from thioamides (propylthiouracil or methimazole) typically presents with sore throat and fever 1
• If fever develops during antithyroid drug therapy, obtain a complete blood count immediately and discontinue the thioamide 1
• Other drug side effects include hepatitis and vasculitis, which can also cause fever 1

Diagnostic Approach for Fever in Hyperthyroid Patients

Immediate Assessment

• Evaluate for thyroid storm criteria: fever, tachycardia disproportionate to fever, altered mental status, and cardiovascular instability 1, 2
• Examine the thyroid for tenderness, enlargement, or nodules suggesting thyroiditis 3, 4
• Check complete blood count to exclude agranulocytosis if patient is on antithyroid drugs 1
• Measure erythrocyte sedimentation rate, which is elevated in subacute thyroiditis 3, 4

Confirmatory Testing

• Obtain serum TSH, free T4, and T3 to confirm hyperthyroid state and assess severity 6, 7
• If thyroid storm is suspected, do not delay treatment for test results—initiate therapy immediately 1
• Consider thyroid antibody testing (antithyroglobulin, antimicrosomal) if autoimmune thyroiditis is suspected 3
• Pursue infectious workup including blood cultures, urinalysis, and chest imaging to exclude concurrent infection 5

Common Pitfalls to Avoid

• Do not attribute 20 days of fever solely to uncomplicated hyperthyroidism—this duration demands investigation for thyroid storm, thyroiditis, infection, or drug reaction 1, 5
• Do not miss thyroid storm by focusing only on fever; look for the constellation of fever, extreme tachycardia, altered mental status, and cardiovascular compromise 1, 2
• Do not continue antithyroid drugs if fever develops without first checking for agranulocytosis, as this complication can be life-threatening 1
• Remember that additional diseases and comorbidities may mask typical symptoms of thyrotoxicosis, making diagnosis more challenging 2