Hypocalcaemia following thyroidectomy for thyrotoxicosis

Temporary postoperative hypocalcaemia is a relatively common complication following thyroidectomy for thyrotoxicosis. Damage, devascularization or inadvertent removal of the parathyroid glands is the most widely accepted reason, but other causes have been postulated including release of calcitonin during operative manipulation and "hungry bone syndrome' due to postoperative reversal of thyrotoxic osteodystrophy.

The study included 63 patients who had subtotal thyroidectomy, 51 for thyrotoxicosis and 12 for non-toxic goitre. Ninety-two per cent had at least three parathyroid glands preserved. All had postoperative levels of parathyroid hormone measured.

The incidence of biochemical hypocalcaemia was 46 per cent and that of symptomatic hypocalcaemia was 21 per cent. No patient was hypoparathyroid. The incidence of hypocalcaemia was 27 of 51 in thyrotoxic patients compared with two of 12 in the non-toxic goitre group (P < 0.05).

Hypoparathyroidism does not appear to be the main reason for hypocalcaemia after thyroidectomy, and other causes such as "hungry bone syndrome' may be important contributory factors.