The utility of intact parathyroid hormone level in managing hypocalcemia after thyroidectomy in children

Abstract

IntroductionHypocalcemia is a common complication after thyroidectomy. Intact parathyroid hormone (PTH) has been successfully used as a predictive indicator for hypocalcemia in adults during the postoperative period. We aim to demonstrate the utility of PTH in predicting and managing postoperative hypocalcemia following thyroidectomy in pediatrics. MethodsThe study is a retrospective case series including 38 patients up to 18 years of age who underwent total or completion thyroidectomy from 1/1/2010 to 12/31/2016 at a tertiary pediatric academic center. Patient demographics, pathology, postoperative PTH, serum calcium, and length of stay were analyzed. ResultsThe median age was 14.3 years (range of 4.3–18.4 years) with 84.2% being female. Thyroid malignancy was noted in 25 patients, and 13 had benign pathology including 8 patients with multinodular goiter and 5 with Grave's disease. In this serie, 63.2% (24/38) developed hypocalcemia (serum calcium <8.5 mg/dL) postoperatively. The median PTH of 15.8 pg/mL in the hypocalcemic group was significantly lower than the median PTH of 41.6 pg/mL in the normocalcemic group (p < 0.001). Using a PTH threshold of 26 pg/mL, hypocalcemia was predicted with a sensitivity of 75%, and specificity of 100%. Six patients with calcium <7.5 mg/dL received teriparatide injections to avoid intravenous calcium replacement. The length of hospital stay for normocalcemic patients was 1.7 ± 0.8 days vs. 2.9 ± 1.4 days for hypocalcemic patients (p = 0.002). We found no correlation between the incidence of hypocalcemia and pathologic indication for surgery. Completion thyroidectomy was associated with a lower risk of hypocalcemia when compared to total thyroidectomy (p = 0.01) and neck dissections carried an increased risk of postoperative hypocalcemia (p = 0.04). ConclusionPostoperative PTH level has an excellent specificity in predicting hypocalcemia in this pediatric cohort using a threshold of PTH ≤ 26 pg/mL. Those with PTH >26 pg/mL may avoid hypocalcemia by oral calcium replacement with outpatient follow-up. We did not identify a reliable PTH cutoff value above which pediatric patients may be safely discharged immediately following surgery. Adult guideline or pathways that advocate for outpatient thyroidectomy surgery based on normal PTH ≥10 pg/mL in the recovery room may not apply to children.