Endocrine Abstracts

Introduction: Thymic enlargement (TE) due to thymic hyperplasia is known to be associated with Graves’ Disease (GD) and other autoimmune conditions. The incidence is not known. Increasingly, it is identified incidentally on imaging investigating unrelated symptoms. There is no consensus on TE management or follow-up.

Cases: We present three cases of TE and GD.

Case 1: 25-year-old male. Diagnosed with GD after experiencing sweating and tachycardia, biochemistry confirmed thyrotoxicosis, TSH <0.01 Free T4 56.3 (9 – 19 pmol/l), Free T3 >30.72 (3 – 5.4 pmol/l), and TSH Receptor antibodies (TRABs) 28.7 U/l. Treated with Carbimazole. Two months prior, a CT Aortogram performed for chest pain revealed TE. Six-month interval imaging is planned.

Case 2: 51-year-old female, diagnosed with GD was managed with Carbimazole. TSH <0.01, Free T4 38.2, Free T3 20.1, and TRABs 10.1 U/l. Presenting with chest pain, investigations identified an anterior mediastinal mass on CT Aortogram. CT Thorax confirmed radiologic features in keeping with benign TE.

Case 3: 27-year-old female, presented with palpitations, shortness of breath and haemoptysis underwent CT Pulmonary Angiogram revealing a 4.5 x 3.3 cm anterior mediastinal soft tissue mass representing TE. Biochemistry then confirmed GD; TSH <0.01, Free T4 42.6, Free T3 >30.72, and TRABs 17.1 U/l. Managed with Carbimazole and Propranolol. The thymus reduced in size (3.5 x 2.2 cm) on MRI Thorax four months later.

Conclusion: TE associated with GD is thought to be related to thyrotoxicosis and autoimmunity. We recommend undertaking thyroid function and TRABs to exclude GD as a potential cause when TE is identified incidentally on imaging, this will avoid inappropriate invasive procedures (biopsy or surgery). If the initial imaging did not reveal worrying thymic features including irregular borders, local invasion, heterogenicity or cystic changes, conservative management and interval thoracic imaging is recommended once thyrotoxicosis is controlled.