[Post-thyroidectomy hypocalcemia: clinical and laboratory findings]

Hypocalcaemia is a possible sequela of thyroidectomy, the causes of which are not fully understood. Today, correct surgical technique is the most important factor in decreasing the incidence of hypocalcaemia. We analysed 1223 patients (930 total thyroidectomies, 293 hemi-thyroidectomies) treated in our institute from January 1995 to July 2003. Serum calcium, ionized calcium, parathyroid hormone and phosphoraemia were screened pre- and postoperatively. Hypocalcaemia, as defined by a serum calcium concentration below 8.5 mg/dL, occurred in 241 patients (25.1%). In 90.9% of these patients, serum calcium was normal 7 days after thyroidectomy. In three patients we registered permanent hypoparathyroidism 180 days after thyroidectomy. We found a statistically significant difference in the incidence of hypocalcaemia between patients treated for benign disease and those treated for malignant disease with a greater incidence in the latter group (P < 0.05). Several factors are important in determining the incidence of post-thyroidectomy hypocalcaemia but the inadvertent excision of the parathyroid gland, ischaemia and injury are the main causes of the lowering of serum calcium concentrations.