Intraoperative parathyroid hormone levels in thyroid surgery are predictive of postoperative hypoparathyroidism and need for vitamin D supplementation.

BACKGROUND: Intraoperative parathyroid hormone (ioPTH) levels are not monitored routinely in thyroid surgery, although they are used widely during parathyroidectomy as an indicator of parathyroid gland function. This prospective study evaluated the occurrence of hypoparathyroidism after thyroid surgery and the use of ioPTH levels to predict the need for postoperative vitamin D supplementation.

METHODS: Seventy-two patients underwent thyroidectomy or neck dissection by 1 surgeon. Forty-five patients had a total thyroidectomy, 16 patients had a hemithyroidectomy, 9 patients had a completion thyroidectomy, and 2 patients had a neck dissection alone for recurrent thyroid cancer. ioPTH and serum calcium (SCa) levels were obtained during the course of surgery and 1 month after surgery. Levels from these time points were compared, and correlated with the need for vitamin D supplementation at the 1-month follow-up evaluation using the Fisher exact test.

RESULTS: Of the 72 patients, 14 had an ioPTH level less than 10 pg/mL at closure. At the 1-month evaluation, 11 of these 14 patients required vitamin D supplementation because of persistent hypoparathyroidism or hypocalcemia (P <.001). The remaining 3 of the 14 patients with ioPTH levels less than 10 pg/mL at closure did not require vitamin D supplementation at the 1-month evaluation because they were asymptomatic and their PTH and SCa levels had normalized. None of the 58 patients with an ioPTH level greater than 10 pg/mL at closure needed vitamin D supplementation at the 1-month follow-up evaluation.

CONCLUSIONS: An ioPTH level less than 10 pg/mL at closure is a strong predictor of hypoparathyroidism after thyroid surgery. Patients with ioPTH levels less than 10 pg/mL at closure should be placed on vitamin D supplementation after surgery to anticipate decreased parathyroid gland function and to avoid symptomatic hypocalcemia.