Hypoparathyroidism is one of the most common complications of thyroid surgery. There is significant controversy in calcium management practices post thyroid surgery. The drop in PTH levels has been used to predict the likelihood of hypocalcaemia after thyroid surgery. But how reliable is this marker and what is the optimal cut-off that determines the need for calcium supplements? An ENT team in Canada developed a PTH-based postop hypocalcaemia management guideline for patients undergoing total or completion thyroidectomy. The aim of this study was to evaluate whether this algorithm could reduce the use of calcium supplements and the length of stay in hospital. They looked at 95 patients that had undergone total or completion thyroidectomy pre-implementation of the algorithm. By looking at PTH levels two hours postoperatively in the recovery unit, they found that PTH levels of 1.5 pmol/L (14.1 pg/ml) or less had a 99% specificity in ruling in hypocalcaemia, whereas a PTH of 2.8 pmol/L (26.4 pg/ml) or more was set as the threshold that could reliably rule out hypocalcaemia with 96% sensitivity. After implementing the protocol, hypocalcaemia occurred only in 3.1% of cases with PTH >2.8 pmol/L. There was also a reduction of oral calcium over supplementation, as well as a statistically significant reduction in the length of stay in hospital. This study indicates that by using PTH, early discharge may be possible by avoiding prolonged serial calcium measurements and without missing any patients with hypocalcaemia. The main limitation that makes replication of the findings elsewhere complicated is that PTH measurements are not universal and show significant inter-institution variability. The authors highlight this limitation in their article and advocate for the development of institution-specific protocols.
How reliable are PTH levels for the prediction of hypocalcaemia after thyroid surgery?
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