Thymic hyperplasia is accurate to detect new-onset Graves' hyperthyroidism and resolves after restoring euthyroidism

Area of Science:

• Endocrinology
• Internal Medicine
• Radiology

Background:

• Graves' disease (GD) is an autoimmune disorder characterized by hyperthyroidism.
• New extrathyroidal manifestations, including thymic hyperplasia (TH), abnormal liver blood tests (ALBTs), neutropenia (NEU), and Graves' orbitopathy (GO), are increasingly recognized in GD.
• The diagnostic utility of TH in distinguishing GD from other causes of thyrotoxicosis requires further investigation.

Purpose of the Study:

• To evaluate the accuracy of thymic hyperplasia (TH) in differentiating Graves' disease (GD) from non-GD thyrotoxicosis.
• To compare the diagnostic performance of TH with other extrathyroidal manifestations: ALBTs, NEU, and GO.
• To investigate the clinical outcomes and resolution patterns of GD-associated TH and non-GD-associated TH.

Main Methods:

• Prospective analysis of 264 adult patients with newly diagnosed thyrotoxicosis (January 2018 - June 2023).
• Thymic hyperplasia (TH) detection via neck ultrasound (nUS) and confirmation/follow-up with magnetic resonance imaging (MRI).
• Calculation of sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) for GO, TH, ALBTs, and NEU in distinguishing GD from non-GD.

Main Results:

• Thymic hyperplasia (TH) was significantly more prevalent in Graves' disease (GD) (16.4%) compared to non-GD thyrotoxicosis (1.4%) (p < 0.001).
• TH demonstrated high diagnostic accuracy for GD, with a specificity of 98% and a positive predictive value (PPV) of 91%.
• TH resolved in 18 out of 20 GD patients within 12 months of achieving euthyroidism; thymus also resolved in non-GD patients upon euthyroidism.

Conclusions:

• Thymic hyperplasia (TH) is a valuable indicator with a high positive predictive value (PPV) for diagnosing Graves' disease (GD) in hyperthyroid patients.
• A conservative management approach is recommended for thyrotoxicosis-associated TH.
• The resolution of TH following successful treatment of hyperthyroidism suggests its reversible nature and association with the underlying thyroid status.