Endocrine Abstracts

A 62-year-old man with insulin treated type 2 diabetes presented with atrial fibrillation. Despite anticoagulation he suffered an embolic cerebellar infarct ten days later. He was found to have abnormal thyroid function tests (TSH 7.75 mu/l, free T4 49.3 pmol/l, free T3 12.0 pmol/l). Thyroid function test analysis was repeated in a second laboratory confirming the results above. TSH was stimulated by thyrotrophin releasing hormone, confirming thyroid hormone resistance. Magnetic resonance imaging of the pituitary was unremarkable.

Thyroid hormone resistance is inherited in an autosomal dominant manner. Our patient had a twin brother. The twin had a remarkably similar medical history. He had insulin treated type 2 diabetes, atrial fibrillation and had suffered a posterior circulation stroke with left cerebellar infarction in 2005. Thyroid function test were performed and results were consistent with thyroid hormone resistance (TSH 6.67 mu/l, free T4 39.1 pmol/l, free T3 13.1 pmol/l).

Our patients exhibit differential tissue sensitivity to thyroid hormone. They have generalised thyroid hormone resistance with the exception of the heart. This resulted in both patients developing atrial fibrillation complicated by cerebellar infarction. Although the twins are genetically identical it is remarkable and revelling that they have such a similar medical history.