Primary hyperparathyroidism after radioactive iodine therapy: Is it a distinct clinical entity?


      • 2.5% of patients undergoing parathyroidectomy had radioactive iodine exposure.
      • The average latency to development of RAI-induced hyperparathyroidism is 24 years.
      • As age at the time of RAI treatment increases, the latency period decreases.
      • Follow-up serum calcium level every 3–5 years following RAI treatment is recommended.



      Radioactive iodine (RAI) treatment is considered a rare cause of primary hyperparathyroidism (pHPT).


      A multi-institutional retrospective review of patients with pHPT who underwent parathyroidectomy from 1990 to 2020 was completed to evaluate the prevalence and latency time for development of RAI-associated pHPT and determine clinical differences in pHPT patients with or without prior RAI treatment.


      1929 patients with sporadic pHPT underwent parathyroidectomy; 48 (2.5%) had prior RAI treatment and 1881 (97.5%) did not. RAI treatment was for thyrotoxicosis in 43 (90%) patients. Average latency was 24 years (3–59 years) and inversely correlated with age. Patients with prior RAI treatment had lower preoperative calcium and PTH levels (p < 0.0001). No significant differences were observed in age, symptoms, pathology, ectopic glands and cure rate.


      RAI is a potential causative factor for pHPT, accounting for 2.5% of sporadic pHPT. RAI-associated pHPT may be a less severe form of sporadic pHPT and latency inversely correlates with age.


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