Serum PTH at 4 h after total thyroidectomy as a predictor of hypocalcemia: a prospective time frame analysis in search of evidence.

Introduction: There has not been a universal agreement about the timings and the threshold level of PTH that can accurately predict the risk of hypocalcemia. Our study aimed to investigate the changes in the serum PTH levels at various time intervals and correlate it with the development of subsequent hypocalcemia.

Materials And Methods: All patients had a pre-operative serum PTH done and were again assessed intra-operatively, at 4 h, 24 h, 72 h, and 1 month after the thyroid surgery. Absolute serum PTH value at various time points, absolute change in serum PTH values compared to pre-operative level, and relative change (percentage change) in serum PTH values compared with pre-operative levels were used to predict post-operative Hypocalcemia.

Results: 49 patients were included in the study. The sensitivity and negative predictive value was 100% for serum PTH at 4 h. There was a statistically significant difference between the groups that required calcium supplementation versus the group that did not require it. The maximum relative reduction in serum PTH value with respect to the pre-operative level occurred at 4 h in the calcium supplement required group which was 82.5%. Use of combination of 4 h serum PTH and relative change at 4 h yielded the best results.

Conclusion: A combination of absolute serum PTH level at 4 h and the relative decline in serum PTH at 4 h has the highest diagnostic accuracy. The use of this combined parameter helps to reliably predict patients who would require supplementation.