Atypical Subacute Thyroiditis without Thyroid Dysfunction: A Report of Two Cases.

Area of Science:

• Endocrinology
• Internal Medicine
• Thyroidology

Background:

• Subacute thyroiditis (SAT) is a painful thyroid inflammation typically causing transient thyrotoxicosis, followed by hypothyroidism and recovery.
• Current diagnostic criteria for SAT, such as those from the Japan Thyroid Association, often rely on thyroid function test abnormalities.

Purpose of the Study:

• To report two rare cases of subacute thyroiditis (SAT) that presented with characteristic clinical and ultrasound findings but maintained normal thyroid function tests throughout their course.
• To emphasize that euthyroid states do not exclude a diagnosis of SAT, even when current diagnostic criteria are not fully met.

Main Methods:

• Case report of two patients presenting with anterior neck pain, tender thyroid nodules, elevated inflammatory markers, and characteristic ultrasound findings suggestive of SAT.
• Monitoring of thyroid function tests (thyroid-stimulating hormone, free T4, free T3) and serum thyroglobulin levels throughout the clinical course.

Main Results:

• Both patients exhibited symptoms and imaging findings consistent with SAT, including neck pain, thyroid tenderness, elevated inflammatory markers, and specific ultrasound features.
• Despite these findings, both patients remained euthyroid, with normal thyroid function tests, throughout their entire disease course.
• One patient showed an elevated serum thyroglobulin level, a marker sometimes associated with thyroid inflammation.

Conclusions:

• These cases represent rare euthyroid presentations of subacute thyroiditis (SAT).
• The findings challenge the strict reliance on thyroid function tests for SAT diagnosis and suggest that normal thyroid function does not rule out SAT.
• Physicians should consider SAT in the differential diagnosis of neck pain and thyroid inflammation, even in the absence of overt thyroid dysfunction.