PURPOSE: Persistent hypoparathyroidism (hypoPT) is a major complication of total thyroidectomy. Nonetheless, previous reports may have underestimated the prevalence of hypoPT due to patient selection bias. We aimed to estimate the actual prevalence of persistent hypoPT after total thyroidectomy and to find predictive factors for postoperative hypoPT.
METHODS: This study retrospectively reviewed data from a health insurance claims-based database provided by the Japan Medical Data Center Co., Ltd. From 2009 to 2019, 2388 patients who underwent total thyroidectomy were identified using the medical procedure codes. Persistent hypoPT was defined as the prescription of active vitamin D supplements for >1 year postoperatively and the assignment of hypoPT codes.
The prevalence of persistent hypoPT was estimated at two different levels: minimum and maximum estimations with or without postoperative osteoporosis and/or renal failure codes. Correlates for persistent hypoPT were investigated among several demographic and clinical variables.
RESULTS: Of the 2388 patients, 1752 (73.4%) were women with a mean age of 45 years.
The types of diseases were: benign thyroid disease (n = 235), malignant thyroid tumors (n = 1570), Graves ' disease (n = 558), and malignancy combined with Graves' disease (n = 25). The minimum and the maximum estimation of the prevalence of persistent hypoPT were 15.0 and 20.3%, respectively. Multivariate logistic regression analysis showed that the malignant tumor (odds ratio, 1.8) independently correlated with persistent hypoPT.
CONCLUSIONS: The prevalence of persistent hypoPT after total thyroidectomy estimated by the claims-based database was higher than previously recognized. Comprehensive attempts to preserve parathyroid function, especially in malignant diseases, are essential.