Long-term effects on parathyroid function and risk factors for permanent hypoparathyroidism in post-surgical differentiated thyroid cancer patients treated with 131I: a retrospective analysis of clinical data

This study aims to explore the long-term effects on parathyroid function and risk factors associated with permanent hypoparathyroidism (HPT) in differentiated thyroid cancer (DTC) patients treated with 131I. 201 postoperative DTC patients were included. Serum levels of parathyroid hormone (PTH), 25-hydroxyvitamin D (25-OH-VD), calcium (Ca), phosphorus (P), and alkaline phosphatase (ALP) were collected before (baseline) and after 131I treatment. Patients were divided into permanent HPT group and non-permanent HPT group, and risk factors were analyzed using penalized logistic regression (PLR). There were no statistically significant differences in serum levels of PTH, 25-OH-VD, Ca, P, and ALP among the five time points (baseline, 6 months, 12 months, 24 months, and 36 months) (P > 0.05). Multivariate PLR analysis revealed that the presence of functional metastases in the first 131I-SPECT/CT-whole-body scan (131I-WBS) was a significant risk factor for permanent HPT (OR = 21.392, P < 0.05). Postoperative 131I therapy for DTC has no significant adverse effects on the parathyroid function within three years, but extremely few patients still develop permanent HPT, with an increased risk in those with functional metastases in the first 131I-WBS.