Hyperparathyroidism due to an intrathyroidal parathyroid adenoma presenting with 2:1 heart block.


AN Comninos, FF Palazzo, R Kaushal


Department of Endocrinology, West Middlesex University Hospital


AIM: To increase awareness of hypercalcaemia-induced cardiac electrical disturbances.


An 85 year old Caucasian male was admitted to hospital with a several week history of confusion, constipation, episodic urinary retention, reduced appetite, dizziness and frequent falls. He was known to the endocrine clinic with a diagnosis of primary hyperparathyroidism but had previously been asymptomatic. The corrected calcium (CCa) ranged from 2.8 to 3.1 mmol/L (NR 2.15-2.6 mmol/L), with an inappropriate parathyroid hormone (PTH) of 107 pg/mL (NR 1.06-6.89 pg/mL) and a Vitamin D of 60 ng/mL (NR >20 ng/mL).


On admission he was bradycardic at 32 bpm with a significant postural blood pressure drop. Examination of the neck, cardiovascular, abdominal, respiratory, and neurological systems was otherwise normal. 


An ECG revealed new onset 2:1 Heart Block.


His blood tests showed marked hypercalcaemia: CCa 3.48 mmol/L, PO4 0.53 mmol/L, Magnesium 0.71 mmol/L, eGFR 70 mL/min.


He was initially rehydrated and then given IV pamidronate. He went back into sinus rhythm when his calcium reached 2.8 mmol/L. However the calcium gradually increased and there was further 2:1 heart block. He was monitored on the Coronary Care Unit and had a permanent pacemaker inserted.


Parathyroid localisation studies were performed and the Sestamibi scan revealed appearances consistent with a left parathyroid adenoma. He was transferred for specialist endocrine surgery where due to the neck anatomy (including an enlarged thyroid gland) he underwent an open parathyroidectomy. A normal left inferior parathyroid gland was identified but no superior gland despite prolonged exploration.  Based on the preoperative imaging the decision was taken to perform a left hemithyroidectomy for a possible intrathyroidal parathyroid, which was later confirmed histologically.


Post operatively the calcium rapidly returned into the normal range and he made a good recovery. On latest follow-up his serum calcium remains normal and he remains in sinus rhythm. His physical and mental status have returned to normal with restoration of normocalcaemia.


This case highlights the varied presentation of severe hypercalcaemia. Patients presenting with arrhythmias should have their calcium levels checked routinely. In addition this case provides an example of the uncommon intra-thyroidal parathyroid.