[Effect of ¹³¹iodine therapy on parathyroid function in postoperative patients with papillary thyroid carcinoma]

Objective: To investigate the impact of postoperative iodine-131 (¹³¹I) therapy on parathyroid function in patients with papillary thyroid cancer (PTC) who did not develop hypoparathyroidism after total thyroidectomy. Methods: A retrospective analysis was conducted on patients with PTC who underwent total thyroidectomy followed by ¹³¹I therapy at the Fourth Hospital of Hebei Medical University between March 2016 and December 2023. Enrolled patients had no postoperative hypoparathyroidism and all received a fixed dose of ¹³¹I therapy. Changes in parathyroid hormone (PTH) and serum calcium levels were analyzed before ¹³¹I therapy and at 1, 3, 6, and 12 months after therapy in the overall population and in subgroups stratified by ¹³¹I dose (100 mCi and 150 mCi groups), sex, age, extent of central lymph node dissection, T stage, N stage, and clinical stage. Statistical analysis was performed using SPSS 25.0 software. Results: A total of 124 patients were enrolled, including 44 males and 80 females, with a mean age of 44.3±11.3 years. No patient developed symptomatic hypocalcemia or hypercalcemia within one year after ¹³¹I therapy. Pairwise comparisons of PTH and calcium levels before and at various time points after treatment in the overall population and all subgroups showed no statistically significant differences (all P>0.05). One patient (1/124, 0.81%) had a serum calcium level of 1.80 mmol/L and PTH of 33.0 ng/L at 12 months and received calcium supplementation. Conclusion: Conventional fixed-dose ¹³¹I therapy after total thyroidectomy does not result in long-term impairment of parathyroid function in PTC patients without baseline hypoparathyroidism. The incidence of hypocalcemia is low, and cases requiring calcium intervention are rare. Parathyroid function is not influenced by ¹³¹I dose, gender, age, extent of central lymph node dissection, T stage, N stage, or clinical stage.