Endocrine Abstracts

A 36 year old man presented with collapse following weakness and vomiting for 2 weeks and 7 kg weight loss over 6 months. Thyroxine 50 mcg OD had been commenced 2 months earlier for hypothyroidism (Free T4 9.4 pmol/l, TSH 8.4 mU/l and anti-TPO antibodies 103.1 IU/mL). Examination found cachexia (weight 53.6 Kg), vitiligo, sinus tachycardia 110 bpm and BP 90/66 mmHg. Investigations: sodium 115 mmol/l, potassium 4.4 mmol/l, urea 9.9 mmol/l, creatinine 81 μmol/l, cortisol 137 nmol/l, aldosterone <100 pmol/l and ACTH 1337 ng/l. Short synacthen test: Cortisol 0 min 137, 30 min 136 and 60 min 142 nmol/l. Adrenal autoantibodies positive. Treatment with intravenous hydrocortisone followed by oral hydrocortisone (10, 5, 5 mg) and fludrocortisone (100 mcg OD) resulted in clinical improvement and normalisation of electrolytes. Shortly before discharge at 6 days he sustained a cardiac arrest with polymorphic ventricular tachycardia, ventricular tachycardia and ventricular fibrillation requiring DC cardioversion 27 times. The admission ECG showed long QTc (530 ms), which was absent 7 years earlier and post arrest. Whilst long QT intervals are common in glucocorticoid deficiency we are aware of only 5 reports of associated ventricular arrhythmias, all of which occurred before treatment. Glucocorticoid deficiency decreases glucocorticoid inducible kinase-1 (SGK1) which controls expression of the hERG gene (human ether-a-go-go related gene). This in turn encodes the alpha subunit of the rapidly activating delayed rectifier potassium channel (I_Kr) which mediates cardiac repolarisation. Hence there is delayed repolarisation with consequent long QT in Addison’s disease. This case demonstrates that life threatening arrhythmias can occur following treatment for Addison’s disease as well as before treatment. Why this occurs in only a minority of cases is unknown. The patient made a remarkable recovery from his experience.