Serum levels of intact parathyroid hormone on the first day after total thyroidectomy as predictor of permanent hypoparathyroidism

Abstract

Background: Permanent hypoparathyroidism is the most common long-term complication after total thyroidectomy, causing significant morbidity and requiring long-term replacement therapy. Our study objective was to assess whether intact parathyroid hormone (iPTH) levels on the first day after total thyroidectomy are a good predictor of permanent hypoparathyroidism.

Patients and methods: A retrospective observational study of all patients undergoing total thyroidectomy between January 2009 and December 2014. iPTH and calcium levels were measured the first day after surgery. Patients were followed up for at least one year after surgery.

Results: The study group consisted of 481 patients with a mean age of 53±14 years, 82% of them females. The most common reason for thyroidectomy was multinodular goiter (75%), followed by papillary thyroid cancer (15%). Transient hypocalcemia was the most common early complication after total thyroidectomy (49%), and permanent hypoparathyroidism was the most common long-term complication (6%). ROC curve analysis showed that iPTH level on the first postoperative day was a good predictor of permanent hypoparathyroidism (area under the curve 0.87; 95% CI: 0.84-0.91). Cut-off iPTH levels of 5pg/mL had 95% sensitivity, 77% specificity, 21.6% positive predictive value, and 99.6% negative predictive value.

Conclusions: iPTH level on the first day after total thyroidectomy is a useful predictor of permanent hypoparathyroidism because of its high negative predictive value. Serum iPTH levels >5pg/mL virtually exclude presence of permanent hypoparathyroidism.

Keywords: Hipocalcemia; Hipoparatiroidismo; Hypocalcemia; Hypoparathyroidism; Parathormone; Paratohormona; Thyroidectomy; Tiroidectomía.