Endocrine Abstracts

Case history: A 65 year-old Caucasian gentleman was admitted with out-of-hospital VF arrest at work place. ROSC was achieved after shock by paramedics but developed multiple in-hospital arrests requiring (>100 shocks in 24 h) with incessant polymorphic ventricular tachycardia which was resistant to anti-arrhythmic therapy including drugs and pacing. Investigations revealed hypercalcemia and newly diagnosed high PTH with no change in mild LV dysfunction from previous myocardial infarction. He finally got stabilised with intubation and ventilation along with hypercalcemia management.

Investigations: Admission bloods revealed mild hypokalemia of 3.3 mmol/l, adjusted calcium was significantly high at 3.18 mmol/l and PTH of 376 ng/l. ECG did not show any evidence of Brugada syndrome or short QT interval. Echo did not show any change from previous one done 2 years back following MI in terms of functional status and valvular function.

Results and treatment: Hypercalcemia was treated with IV fluids and zolendronate infusion followed by cinacalcet. Though hemofiltration was considered with persistent arrythmia, calcium level and arrythmias eventually settled. Patient became hemodynamically stable and calcium level dropped to 2.8 prior to discharge. TFT, metanephrines and calcitonin were normal.

USS neck: multiple nodules in the left thyroid lobe with retrosternal extension. Sestamibi scan showed left thyroid lobe nodule with peripheral calcification but no separate parathyroid adenoma. Intrathyroid parathyroid adenoma was suggested as a possibility. CT CAP was unremarkable except for 2 sub-centimetre lung nodule at lung base. Patient had left hemi-thyroidectomy with a significant drop in intra-operative parathyroid measurement confirming the diagnosis. Histology confirmed intra-thyroidal parathyroid adenoma with incidental finding of minimally invasive follicular carcinoma of Hurthule cell type. Patient awaits completion right hemithyroidectomy.

Conclusions and points for discussion: Hypercalcemia with short QT interval is known to cause ventricular arrythmia but it could occur even in patients with normal QT interval. PTH per se could be arrhythmogenic, triggering ventricular arrhythmia at lower calcium levels. Ectopic parathyroid adenoma can be found as intrathyroidal nodule and is a rare cause of primary hyperparathyroidism. Intrathyroidal parathyroid adenoma can be associated with thyroid malignancy.

This case raises few questions: • What is the pathophysiology of ventricular arrythmia in hyperparathyroid patients with normal QT interval?

• How can we risk stratify the hyperparathyroidism patients at risk of ventricular arrhythmia?

• What are the optimal treatment options in hypercalcemia-induced electric storm?

• What are the appropriate investigations for identification of the thyroid malignancy associated with intrathyroidal parathyroid adenoma?