EP68 – Postoperative PTH compared with IPTH gradient as predictors of post-thyroidectomy hypocalcemia; stratifying patients for outpatient thyroidectomy

      Dhillon, Vaninder1; Al-Khadem, Mai1; Rettig, Eleni1; Tufano, Ralph P.1,2 1 Department of Otolaryngology, Head and Neck Surgery-Endocrine Surgery Division, Johns Hopkins University, Baltimore, MD, USA 2 Faculty, Chief of Endocrine Surgery Division, Department of Otolaryngology, Head and Neck Surgery-Endocrine Surgery Division, Johns Hopkins University, Baltimore, MD, USA   Background/Purpose: Predicting which patients will not develop symptoms from hypocalcemia after thyroidectomy may allow for same day discharge, even if calcium supplementation is required. Our objective is to assess the utility of pre and one-hour post-operative intact PTH (IPTH) gradient compared to the one-hour post-op IPTH alone to predict risk of severe hypocalcemia, and determine which patients require hospital admission for symptomatic hypocalcemia. Methods: This was a retrospective review of patients who underwent primary total thyroidectomy by the senior author from May 2015 to May 2016. Logistic regression was used to evaluate differences in postoperative calcium and calcitriol supplementation requirement by IPTH gradient, and by quartile of absolute postoperative IPTH. Mild, severe and symptomatic hypocalcemia were defined. Results: Overall, 119 patients were analyzed. 47% of patients developed any postoperative hypocalcemia, including 26 (22%) with mild and 30 (25%) with severe hypocalcemia. Thirteen patients had severe hypocalcemia that resolved with calcium supplementation. Postoperative IPTH and IPTH gradient were highly correlated (p<0.001). IPTH gradient was more strongly associated than postoperative IPTH. IPTH gradient was, however, a significantly better predictor of hypocalcemic symptoms than was postoperative IPTH (AUC 0.75; p=0.03). Risk groups for post-thyroidectomy hypocalcemia were created with high risk: IPTH gradient > 80%. Discussion: IPTH gradient is more significantly associated with severe and symptomatic hypocalcemia compared to postoperative IPTH alone. Conclusion: IPTH gradient > 80% can be used to assess patients at risk for severe and symptomatic hypocalcemic after thyroidectomy, and is a valuable metric to stratify those that require overnight hospitalization from same-day discharge with supplementation.   References:
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