Utility of serum parathyroid hormone measurement as a predictor of post-thyroidectomy hypocalcemia: A single-center observational study

Abstract

Introduction: The prevalence of thyroid cancer is from 4 to 7%; in Ecuador, it reaches a rate of 16/per 100,000 inhabitants; in most cases, it requires surgical resolution associated with a complication rate of 2 to 15%, of this hypocalcemia represents at least minus 10.9%. This study aimed to evaluate the usefulness of measuring serum parathyroid hormone (PTH) as a predictor of hypocalcemia after thyroidectomy.

Methods: An analytical cross-sectional study of patients with thyroidectomy was carried out at the Metropolitan Hospital of Quito from January 2017 to December 2019. Demographic, clinical, surgical, and complication variables were analyzed. PTH's relationship with clinical or serological hypocalcemia or both was compared using PR, sensitivity, specificity, PPV, NPV, and LR. Other confounding variables were analyzed using multinomial logistic regression comparing their ORs.

Results: A total of 212 records were included, 15.6% men and 84.4% women, with an average age of 52.1 years. The main indication for thyroidectomy was papillary carcinoma 123 (58.0%). Complications were 22.7%. A total of 48 patients developed hypocalcemia. PTH levels < 10 ng/l predict hypocalcemia with a sensitivity of 0.55, specificity of 0.78, PPV: 43%, NPV: 85% and PR was 2.91 (95% CI 1.06 - 8.01).

Conclusions: PTH quantification of 10 ng/l or less helps predict clinical hypocalcemia in patients undergoing total thyroidectomy.