Endocrine Abstracts

Introduction: There is no consensus about the management of thymic enlargement in Graves’ disease (GD). If imaging indicates ‘benign’ thymic appearances, and interval scans are stable, most authorities advocate no intervention until thyrotoxicosis is controlled. We present 3 patients with GD and incidentally found thymic enlargement.

Case presentations: a. A 37-year-old female presented acutely with osmotic symptoms, a weight loss of 5 stones and postural symptoms. She was dehydrated, had postural hypotension, a smooth goiter (with loud bruit), but no pigmentation. Investigations showed: free T3 >46.1 pmol/L; free T4 59.5 pmol/L; TSH <0.01 mU/L; TRAb 25.5; corrected calcium 2.98 mmol/L; PTH <0.5 nmol/L; short Synacthen – cortisol 305 nmol/L (0 min) and 343 nmol/L (30 min); adrenal antibodies +ve. CT scans showed benign thymic enlargement. She was rehydrated, given pamidronate and GD and Addison’s disease treated appropriately.

b. A 36-year-old female, was investigated for breathlessness and weight loss. CT showed an anterior mediastinal mass and she was scheduled for biopsy under anaesthesia. Investigations showed free T3 17 pmol/L; free T4 32 pmol/L; TSH <0.02 mU/L and TRAb +ve. On review in the Thyroid clinic, the CT appearances were consistent with benign thymic hyperplasia. She was given carbimazole and surgery postponed.

c. A 47-year-old female presented with breathlessness, chest pain, weight loss and shakiness. CTPA showed benign thymic hyperplasia. Investigation showed free T3 6.7 pmol/L; free T4 18.7 pmol/L; TSH < 0.02 mU/L and TRAb +ve. Her GD was treated appropriately.

Discussion: The true incidence of thymic hyperplasia in GD is unknown but estimated to be 96–97%. Our patients had thymic hyperplasia discovered incidentally. Studies have shown regression in the vast majority of subjects, on treating GD. Therefore if CT appearances are ‘benign’ (an arrowhead appearance, linear margins, isodense with muscle, without calcification or infiltration), thymic biopsy or removal may be postponed till interval scans are done after the control of thyrotoxicosis.