Association of Parathyroid Hormone Level With Postthyroidectomy Hypocalcemia: A Systematic Review

Importance There has been an increased interest in measuring parathyroid hormone (PTH) levels as an early predictive marker for the development of hypocalcemia after total thyroidectomy. However, significant variation exists in the timing, type of assay, and thresholds of PTH in the literature. Objective We performed a systematic review to examine the utility of PTH levels in predicting temporary postthyroidectomy hypocalcemia. Evidence Review A systematic literature review of studies published prior to May 25, 2016 was performed within PubMed, EMBASE, SCOPUS, and Cochrane databases using the following terms and keywords: “thyroidectomy,” “parathyroid hormone,” and “hypocalcaemia,” “calcium,” or “calcitriol.” Each candidate full-text publication was reviewed by 2 independent reviewers and selected for data extraction if the study examined the prognostic significance of PTH obtained within 24 hours after thyroidectomy to predict hypocalcaemia. Studies were excluded if calcium supplementation was used routinely or based on a PTH level. Study characteristics, PTH parameters used to predict hypocalcemia, and their respective accuracies were summarized. Findings The initial search yielded 2417 abstracts. Sixty-nine studies, comprising 9163 patients, were included. Overall, for an absolute PTH threshold, the median accuracy, sensitivity, and specificity were 86%, 85%, and 86%, respectively. For a percentage change over time the median accuracy, sensitivity, and specificity were 89%, 88%, and 90%, respectively. Conclusions and Relevance The existing literature regarding PTH levels to predict postthyroidectomy hypocalcemia is extremely heterogeneous. A single PTH threshold is not a reliable measure of hypocalcemia. Additional prospective studies controlled for timing of laboratory draws and a priori defined PTH thresholds need to be performed to ascertain the true prognostic significance of PTH in predicting postthyroidectomy hypocalcaemia.