A novel index to predict postoperative hypocalcemia in primary hyperparathyroidism

Vitamin D (Vit D) deficiency is common in patients with hyperparathyroidism, but the importance of replacement before surgery is controversial. It can be predicted that hypocalcemia risk will be higher in patients with high bone turnover.

In this study, the effect of preoperative ALP/Vit D ratio on postoperative hypocalcemia was investigated.

Among the primary hyperparathyroidism cases who were operated between 2015 and 2022, 158 patients with complete data were included in the study. Preoperative laboratory results, radiological images, and pathology reports of the patients were evaluated retrospectively. The cross-sectional value of the ALP/Vit D value predicting hypocalcemia was calculated. The effect of these parameters on postoperative hypocalcemia was investigated.

The mean age of our patients was 54 (21-81 years). When factors affecting postoperative hypocalcemia were evaluated by univariable analysis, Vit D deficiency and insufficiency (p < 0.001), ALP (p < 0.001), ALP/Vit D ratio (p < 0.001), and T score (p = 0.026) found to be factors affecting postoperative hypocalcemia. In multivariate analysis, the ALP/Vit D ratio was found to be an independent variable in predicting hypocalcemia. It was found that hypocalcemia was 45 times more common in patients with ALP/Vit D > 6.34 (p < 0.001). ALP/Vit D ratio predicts patients who will develop postoperative hypocalcemia with 87.2% sensitivity and 87.1% specificity.

Vit D deficiency increases the risk of postoperative hypocalcemia, but it is not sufficient alone to predict it. The risk increases more in patients with high bone turnover. The preoperative ALP/Vit D ratio is the strongest predictor of postoperative hypocalcemia risk.