Predictors of persistently elevated parathyroid hormone levels after parathyroidectomy: experience from a reference center.

OBJECTIVE: Primary hyperparathyroidism is considered the third most common endocrine disorder. Moreover, persistently elevated levels of parathyroid hormone occur in up to 30% of patients undergoing parathyroidectomy. The aim of this study was to determine the prevalence of persistently elevated parathyroid hormone levels after parathyroidectomy and analyze its associated factors. METHODS: An anonymized medical record query was conducted, filtering patients who underwent parathyroidectomy at a tertiary hospital center in Southern Brazil from 2010 to 2019. Clinical, laboratory, and sociodemographic data were collected. The analyzed period ranged from 3 months prior to surgery and up to 18 months after surgery. RESULTS: A total of 261 patients with an average age of 56 (45-65) years and a body mass index of 25.53 (22.19-28.86) kg/m2 were included. Patients with normal parathyroid hormone levels after 18 months of surgery were compared to those with high parathyroid hormone levels in the same period. The latter had lower levels of median parathyroid hormone, minimum achieved parathyroid hormone, and higher values of vitamin D. The two groups showed no difference in terms of age, body mass index, parathyroid hormone before parathyroidectomy, calcium before and after parathyroidectomy, and glomerular filtration rate. The multivariate linear regression model showed a negative association between body mass index, glomerular filtration rate, and total calcium after parathyroidectomy with parathyroid hormone variation. Patients with reduced glomerular filtration rate had higher levels of parathyroid hormone before parathyroidectomy, with no significant difference after the procedure between glomerular filtration rate groups. CONCLUSION: Persistently elevated levels of parathyroid hormone occurred in more than half of the patients subjected to parathyroidectomy. The observed variation in parathyroid hormone was significantly higher in patients with reduced glomerular filtration rate.