Dynamics of PTH levels in the development of post-operative hypoparathyroidism.

Background: Post-operative hypoparathyroidism is the most frequent complication after total thyroidectomy. The identification of preoperative predictors could be helpful to identify patients at risk. This study aimed to evaluate the potential influence of preoperative PTH levels and their perioperative dynamics as a predictor of transient, protracted, and permanent post-operative hypoparathyroidism.

Methods: A prospective, observational study that includes 100 patients who underwent total thyroidectomy between September 2018 and September 2020.

Results: Transient hypoparathyroidism was present in 42% (42/100) of patients, 11% (11/100) developed protracted hypoparathyroidism, and 5% (5/100) permanent hypoparathyroidism. Patients who presented protracted hypoparathyroidism had higher preoperative PTH levels. The protracted and permanent hypoparathyroidism rate was higher in groups with greater preoperative PTH [0% group 1 (<40 pg/mL) vs. 5.7% group 2 (40-70 pg/mL) vs. 21.6% group 3 (>70 pg/mL); p = 0.03] and (0 vs. 8.3 vs. 20%; p = 0.442), respectively. The rate of protracted and permanent hypoparathyroidism was higher in patients with PTH at 24 h lower than 6.6 pg/mL and whose percentage of PTH decline was higher than 90%. The rate of transient hypoparathyroidism was higher in patients who showed a PTH decline rate of more than 60%. The percentage of PTH increase one week after surgery in patients with permanent hypoparathyroidism was significantly lower.

Conclusion: The prevalence of protracted hypoparathyroidism was higher in groups with higher preoperative PTH levels. PTH levels 24 h after surgery lower than 6.6 pg/mL and a decline of more than 90% predict protracted and permanent hypoparathyroidism. The percentage of PTH increase a week after surgery could predict permanent hypoparathyroidism.