Pertechnetate thyroid uptake is not always suppressed in patients with subacute thyroiditis

Area of Science:

• Endocrinology
• Immunology
• Nuclear Medicine

Background:

• Subacute thyroiditis (SAT) presents with clinical features mimicking other thyroid conditions.
• Understanding the immunologic aspects and clinical courses of SAT is crucial for accurate diagnosis and management.
• Thyroid autoantibodies and radioisotope uptake patterns can offer insights into SAT pathophysiology.

Purpose of the Study:

• To investigate the clinical courses and immunologic profiles of patients with SAT-like symptoms.
• To correlate thyroid autoantibody levels with technetium-99m pertechnetate thyroid uptake (Tc-99m uptake) in SAT patients.
• To explore the mechanisms behind varied Tc-99m uptake patterns in SAT.

Main Methods:

• Studied 15 patients with SAT-like clinical features.
• Assessed thyrotropin-binding inhibitory immunoglobulins (TBII) and thyroid stimulating antibody (TSAb) levels.
• Measured Tc-99m pertechnetate thyroid uptake and performed thyroid imaging.
• Monitored serum TSH levels and localized inflammatory processes.

Main Results:

• Two patients with strongly positive TBII/TSAb showed elevated Tc-99m uptake.
• Six patients had partially suppressed or normal Tc-99m uptake with unilateral lobe involvement.
• Seven patients exhibited no Tc-99m uptake, with bilateral lobe inflammation.
• Low TSH levels were detected in some patients; TBII/TSAb were absent in those with no uptake.

Conclusions:

• Marked Tc-99m uptake suppression in SAT is primarily due to follicular cell damage.
• Non-suppressed or elevated Tc-99m uptake in SAT can occur due to Graves' disease association or other mechanisms.
• Immunologic markers and uptake patterns reveal heterogeneity in SAT, necessitating further research.