Abstract
Objective: to detect the effect of anti-thyroid drugs(ATD) on the therapeutic outcome of I-131 in hyperthyroid Graves' patients. Methods: Retrospective study was done on 200 patients with Graves' disease treated with fixed dose of radioactive iodine (RAI) (12- 15mCi). The patients were classified into three groups: Group I (n = 70) were treated by ATDs for more than 6 months and stopped it 5 days; group II (n = 70) were treated by ATDs for more than 6 months but stopped it only for two days or less, and group III (n = 60) had never been treated with ATD before RAI treatment (control group). Results: There was a statistical significant difference in the cure rate between group I and group II (P < 0.001), group II and group III (P < 0.001), but no significant difference between group I and group III (P = 0.453) three months after RAI therapy. There was a statistical significant difference in the cure rate observed between group I and the group II (P =0.002), group II and group III (P < 0.001), but no significant difference between group I and group III (P =0.060) 6 months after RAI therapy. Conclusion: Administration of ATDs more than 6 month without discontinuation decreased response of RAI treatment in 3 and 6 months' follow-up. Discontinuation of ATDs for 5 days before RAI treatment is recommended.