Prospective Evaluation of Predictive Risk Factors of Postoperative Hypocalcemia following Total Thyroidectomy

Abstract

BACKGROUND: Thyroid surgery is the most commonly performed endocrine surgery worldwide. Total Thyroidectomy (TT) is the most common endocrine surgery performed world-wide. Postoperative hypocalcemia still remains common complication after TT, prolonging hospitalization and increasing costs. Hypoparathyroidism secondary to surgery is the commonly attributed cause but other factors attributing hypocalcemia merits evaluation. AIM OF THE STUDY: This prospective observational study aimed to evaluate the predictive risk factors for the development of postoperative transient (lt 6 month) and permanent hypocalcemia (gt 6 months) post-TT. MATERIALS AND METHODS: Consecutive patients (n = 328; age = median (IQR); 34 (15) years; M: F= 65: 263) with benign or malignant thyroid disease undergoing first-time TT were evaluated for serum levels of corrected calcium, phosphorous, magnesium, intact parathyroid hormone, alkaline phosphatase, and 25-hydrocy cholecalciferol at the baseline, 24-hour, 48-hour and six-month after surgery. At-least three parathyroid glands preserved. P lt 0.05 was considered significant. RESULTS: The incidence of postoperative transient hypocalcemia was 57% (n=187), of which 33.5% (n= 110) were symptomatic while 23.5% (n=77) were asymptomatic and preoperatively 13.1% had biochemical hypocalcemia [Ca lt 8.4 mg/dL]. Age, gender, surgeon s experience failed to impact. Graves disease and malignancy increased the risk of transient hypocalcemia while thyroiditis was associated with permanent hypocalcemia. CONCLUSION: Serum 24-hour calcium lt 8 mg/dL, 48-hour magnesium lt 1.8 mg/dL, and 48-hour iPTH lt 11.3 pg/mL were independent risk factors for transient hypocalcemia. Percent calcium decline gt 12% and concurrent hypomagnesemia precipitate refractory hypocalcemia necessitating both calcium and magnesium correction for prompt resolution. Serum 48-hour calcium lt 7.8 mg/dL, permanent hypoparathyroidism and thyroiditis were independent risk factors for permanent hypocalcemia at 6 months after total thyroidectomy.