Abstract

Thymic hyperplasia is an uncommon finding in adults, given that the natural course of the gland is atrophy with age (Liang et al., 2022). Its association with hyperthyroidism is also less recognized by clinicians, and thus its incidental finding may sometimes either go unnoticed or evoke concerns of anterior mediastinal malignancy. However, this case study reinforces the finding that thymic hyperplasia in adults with hyperthyroidism is likely a result of the trophic effect of elevated thyroid hormones and the associated Thyroid stimulating hormone Receptor-associated Antibodies (TRAbs) seen in Graves’ disease and should thus not warrant the pursuit of extraneous invasive investigations when malignancy is unlikely. The case focuses on a middleaged African female with chronic cough, shortness of breath, weight loss, palpitations, pretibial edema, resting tremors, and smooth thyroid enlargement. Initial evaluation for cardiopulmonary and infectious causes was negative, and biochemical testing confirmed the highly probable diagnosis of hyperthyroidism with evidence of suppressed Thyroid Stimulating Hormone (TSH) and elevated Free Thyroxine (FT4). Computed Tomography (CT) scan of the chest noted thymic enlargement alongside diffuse thyroid enlargement. Despite the inability to test for TRAbs due to financial constraints, the clinical, biochemical, and radiologic findings strongly suggested Graves’ disease. The case highlights the importance of recognizing thymic enlargement in hyperthyroidism as a benign and potentially reversible manifestation. This awareness enhances integration of clinical and biochemical findings with imaging to correctly diagnose Graves’ disease and avoid misdiagnosing mediastinal malignancy, especially in resource-limited settings. 

Keywords: Thymic yyperplasia, Thymus gland, Enlargement, Graves’ disease, Hyperthyroidism