Early Predictors of Post - Thyroidectomy Hypoparathyroidism.

Thyroid surgery is the most commonly performed procedure in the field of endocrine surgery. Studies are still ongoing on the development of a single algorithm for diagnosis and care of patients at risk of postoperative hypoparathyroidism. The aim of the study was to determine the biochemical marker that would allow the most accurate diagnosis of patient groups at risk of developing hypoparathyroidism and to identify risk factors for this disorder.

MATERIAL AND METHODS: The prospective study included 142 consecutive patients undergoing total thyroidectomy for benign goiter from January 1st 2014 to December 31st 2015. Serum intact parathyroid hormone (iPTH), total calcium (Ca), phosphate (P), and magnesium (Mg) levels have been measured preoperatively and at 1, 6, 24, and 48 h postoperatively.

RESULTS: Clinical symptoms of hypoparathyroidism developed in 25 (17.6%) of 142 patients. The best diagnostic accuracy for hypoparathyroidism based on ROC curves was obtained for iPTH at 6h (AUC 0.942; 95% CI: 0.866-1.000, p<0.001) and its percentage change from baseline ΔiPTH at 6h (AUC 0.930; 95% CI: 0.858-1.000, p<0.001). In an multivariate analysis, the preoperative Ca level higher by 0.1 mmol/l, and iPTH level higher by 0.1 pmol/l were associated with a lower risk of hypoparathyroidism, by 68% (p=0.012) and 61% (p=0.007), respectively. A 1% decline in iPTH from baseline increased the risk of hypoparathyroidism by 15% (p<0.001).

CONCLUSIONS: The most reliable markers indicating a high risk of postoperative hypoparathyroidism are the decline in ΔiPTH at 6h by > 65% or iPTH level at 6h <1.57 pmol /l. A postoperative decline in iPTH levels is an independent risk factor for the development of hypoparathyroidism. Preoperative higher concentrations of Ca and iPTH are protective factors for the development of this disorder.