Endocrine Abstracts

Background: Radioactive iodine ¹³¹I (RAI) treatment is an effective definitive treatment of hyperthyroidism, used as a first line or second line treatment.

Aims and objectives

1. To evaluate the response of RAI therapy in Graves’ disease.

2. To determine any factors predicting treatment failure.

Study design: Retrospective study: Materials and methods: Clinical records were reviewed and data were collected about hyperthyroid patients. Thyrotoxicosis was diagnosed on the basis of elevated total T4 (50–110 ng/ml) and/or total T3 (0.87–1.78 ng/ml) values with suppressed TSH. The etiology of hyperthyroidism was established with 99 mTc-pertechnetate thyroidimaging and the gland size was measured with ultrasound. Empirical single dose, approximately 10 mci of I-131 was used for ablation. Ablation was done after stoppinganti thyroid medications for at least 3 days prior to RAI therapy, and drugs were restartedafter 2 days.

Post ablation, biochemical monitoring was done once a month. Successful RAI therapy for hyperthyroidism was defined as clinical and biochemical euthyroid or hypothyroid status (group 1). Treatment failure was defined as persistent of hyperthyroidism even after 6–12 months post-RAI therapy (group 2).

Patientswho underwent RAI ablation for Graves disease and whose complete follow up records available were included in the study. Patients who had toxic adenoma and toxic MNG were excluded from the study.

Results: Total 70 patients were recruited,19 patients were excluded due to incomplete data. Fifty one patients were included. Age at diagnosis of hyperthyroidism was 38 ± 9.7 years. Men to women ratio was 1:6.3. Postablation (mean dose of I-131 9.6 ± 0.8 mci), 32 patients (62.7%) achieved remission (group 1). Among these 30 patients became hypothyroid and 2 patients became euthyroid. Nineteen patients (37.3%) failed to achieve remission(group 2). Time for response ingroup 1 was 4.9 ± 2.2 months. Thyroid gland was larger in size in the group 2 (19.9 ± 6.0 gm) as compared to group 1 (10.4 ± 3.8 gm). Mean age at diagnosis was similar among both the groups (group 1:37.3 ± 7 years vs group 2 : 39 ± 13.3 years). There was no difference in the male to female ratio and pre ablation T3, T4 levels, between the two groups.

Conclusion: Sixty three percent of the patients achieved complete remission with a single dose of I-131 with in 5 months. Larger gland size predicted the treatment failure. No other demographic, and biochemical parameters were different between two groups.