Hypocalcemia Following Thyroid Surgery for Hyperthyroidism


Question

I have a patient who has had thyroidectomy for Graves 3 weeks back. He was admitted initially with fast AF and high output cardiac failure. He had treatment with high dose PTU, propranolol, Potassium Iodide and Warfarin.He was adequately prepared and proceeded to total thyroidectomy.

He developed severe hypocalcaemia ( corrected Ca 1.53 mmol/L), and has required continous infusion of Calciem gluconate and 8 gm elemental cacim orally to keep his Calcium around 1.9 mmol/L and symptom free, for 3 weeks post operatively. His Mg initially was low and is now in the normal range on oral Mg replacement. Phosphate has been high between 1.55 to 1.93 mmol/L.. His 24 hour urine Ca with a paired serum Ca of 1.9 mmol/L was low at 2.2mmol/24 hrs (NR 2.5 -7.5). He has been receiving 2 micrograms a day of alpha calcidol.

It seems as though he has hungry bone syndrome. Serum PTH is awaited. He was non compliant with ATD for about 4 years prior to developing high output heart failure and AF. I am not entirely sure what to do next. Is it just a question of time before his calcium normalises or is there any other modalities of treatment? Dr S.P., England

Response

While it is always important to avoid coming to premature closure and to fully consider the differential diagnosis of hypocalcemia, in this instance the described clinical situation is classic for surgically-induced hypoparathyroidism. Most likely the parathyroids were inadvertendly removed or traumatized during neck surgery. As such, I would expect the pending PTH level to be low, or inappropriately 'low-normal' in the face of hypocalcemia. Treatment would typically involve calcitriol and calcium, with related issues more fully described in the Endotext chapter. In followup, one should consider the possibility that traumatized parathyroid tissue can sometimes recover function over a period of weeks or months. Andrew Arnold, MD