Evaluating the Role of Serum Diiodotyrosine in Differentiating Destructive Thyroiditis from Graves’ Disease
Bhoomika Kauloorkar, Sumana Kunnuru, Beatrice Anne, Noorjahan Mohd, Kaushik Puranam, Vijay K. KutalaAbstract
Introduction:
Differentiating Graves’ disease (GD) from destructive thyroiditis (DT) is essential for appropriate management, but clinical overlap complicates diagnosis. Diiodotyrosine (DIT), released during follicular disruption, may serve as a mechanistically distinct biomarker. This study evaluated serum DIT’s diagnostic performance in differentiating DT from GD compared with established markers.
Methods:
Participants included 38 patients with GD, 28 with DT and 18 healthy controls. Diagnosis was based on clinical evaluation, biochemistry, thyrotropin receptor antibody (TRAb) assay and technetium-99m scintigraphy. Serum DIT was quantified using liquid chromatography–tandem mass spectrometry. ROC analysis determined diagnostic cutoffs and performance metrics.
Results:
Median serum DIT levels were significantly higher in the DT group (234.1 pg/mL, IQR 145.1–321.5) than in the GD (176.3 pg/mL, IQR 110.0–257.6) and control (92.1 pg/mL, IQR 45.9– 108.3) groups. DIT demonstrated moderate discriminatory performance (AUC 0.701), with 70% sensitivity and 75% specificity at a 150 pg/mL cutoff. TRAb and technetium uptake showed superior performance (AUC 0.97 each). Serum DIT correlated inversely with TRAb levels (r = −0.276,
Conclusion:
Serum DIT levels reflect follicular disruption and are elevated in DT. While inferior to TRAb and scintigraphy as a standalone test, DIT provides mechanistically complementary information and may serve as an adjunctive biomarker when conventional investigations are inconclusive, unavailable or contraindicated. Population-specific validation is required before routine implementation.