Endocrine Abstracts

Introduction: Hypoparathyroidism is one of the most common complications following thyroidectomy and it is associated with significant morbidity. It usually occurs within the first 48 h after thyroid surgery, however hypocalcemia symptoms may only begin up to 64 h after surgery. Therefore, early detection of hypoparathyroidism is essential to a secure postsurgery discharge.

Objectives: We aimed to evaluate the potential risk factors for postsurgical hypoparathyroidism and to determine the role of early determination of serum parathyroid hormone (PTH) following thyroid surgery to predict the occurrence of postsurgical hypoparathyroidism.

Methods: Retrospective analysis of patients submitted to thyroid surgery between August/22 and July/23 at Hospital CUF Descobertas, Lisbon. Serum PTH and calcium levels were determined 6 hours postoperatively. Hypoparathyroidism was defined as an inappropriately low PTH level (PTH normal range 18.5–88 pg/ml) in the context of hypocalcemia (calcium normal range 8.5–10.1 mg/dl), and it was classified as definitive if persisted longer than 6 months. Patients with a follow-up <6 months and with pre-operative abnomal phospho-calcium metabolism were excluded.

Results: We included 76 patients, 82% female (n=62), with an average age of 52±12years (23–75). 74 patients were submitted to thyroidectomy (lymph node dissection: 7 unilateral, 2 bilateral and 2 central) and 2 to thyroidectomy completion. Thyroid cancer was present in 24 patients (32%). Nineteen patients developed hypoparathyroidism (25%): 14 transient (18%) and 5 definitive (7%). These patients had lower early postoperative PTH levels (5.6±3.8 vs 21.3±16.4 pg/mL, P<0.001), lower postoperative calcium levels (8.3±1.1 vs 8.7±0.5 mg/dL, P=0.026) and had incidental parathyroidectomy more frequently (66.7% vs 19.4%, P=0.002). There were no significant differences among patients with or without postsurgical hypoparathyroidism regarding sex, age, type of thyroid disease (benign or malignant), neither on surgery type (with or without lymph node dissection). ROC-curve analysis revealed a good accuracy for PTH levels measured 6 hours after surgery to rule out the late occurrence of transient or definitive hypoparathyroidism (AUC 0.908 (CI 95% 0,832-0,983)). In all patients with postoperative PTH levels below 4pg/mL hypoparathyroidism was confirmed (29% of these corresponding to definite hypoparathyroidism), while for 6h-postoperative PTH levels above 18.75 pg/ml transient or definitive hypoparathyroidism has never occurred.

Conclusion: Early postsurgical PTH levels represent a simple and useful tool for a rapid evaluation of hypoparathyroidism risk following thyroid surgery. It allows for selective and appropriate calcium and vitamin D supplementation, preventing symptomatic hypocalcemia and reducing delays on hospital discharge.