Role of Postoperative Intact Parathyroid Hormone Levels in Predicting Hypocalcaemia after Thyroidectomy.

ABSTRACT

OBJECTIVE: To determine the sensitivity and specificity of intact parathyroid hormone (iPTH) levels in predicting hypocalcaemia after thyroidectomy. STUDY DESIGN: A descriptive cross-sectional study. Place and Duration of the Study Department of General Surgery, Shifa International Hospital and Shifa Foundation, Islamabad, from May 2021 to 2022. METHODOLOGY: The sample size was calculated to be 205 with consecutive non-probability sampling. Serum iPTH levels and serum calcium levels were measured postoperatively at 6 hours and 24 hours and recorded in a proforma for analysis. After collection, the data were entered and analysed using SPSS version 24.0. RESULTS: Among 205 patients, 157 (76.6%) were females and 48 (23.4%) were males. At 6 hours postoperatively, 121 (59%) patients had normal iPTH levels and 123 (60%) patients had normal serum calcium levels (p = 0.15). At 24-hour, 130 (63.4%) patients had normal iPTH levels and 92 (44.9%) patients had normal serum calcium levels (p = 0.001). Overall, 8 (3.9%) patients developed symptomatic hypocalcaemia (p = <0.001). The sensitivity and specificity of iPTH levels at ≤15 pg/ml were 100% and 70%, respectively, but at 24 pg/ml cut-off level, the specificity increased to 90% with sensitivity of 100%. CONCLUSION: Low serum iPTH levels at 6 hours after surgery can predict hypocalcaemia in patients undergoing thyroidectomy, even if serum calcium levels appear normal at that time. KEY WORDS Parathyroid hormone, Serum calcium, Hypocalcaemia, Total thyroidectomy, Calcium homeostasis.