Endocrine Abstracts

Introduction: Graves’ disease (GD) is a systemic autoimmune disease characterized by lymphocyte activation and synthesis of anti-TSH receptor antibodies (TRABs). Higher values of TRABs are associated with a higher risk of Graves’ ophthalmopathy and dermatopathy. Iodine-131 therapy (RAI) is one of the well-established options in GD, but it can cause a transient increase in TRABs.

Objectives: To evaluate the evolution of TRABs after RAI; to identify factors associated with a more marked increase in TRABs.

Material and methods: Retrospective analysis of a sample of patients with GD undergoing RAI. Information on demographic data, antithyroid drug therapy (ATD), TRAB values over time (pre-RAI and at 1, 3, 6 and 12 months after RAI) and response to RAI were collected.

Results: We analyzed 86 episodes of RAI, involving 75 patients, mostly female (80.0%), 84.9% corresponded to 1^st therapies and 15.1% to subsequent therapies. Age at RAI administration was 40.9±17.2 years, mean 3.0±3.0 years after diagnosis, and 82.6% were under ATDs. The pre-therapeutic TRABs had a median value of 8.0±17.5 U/l (reference range < 1U/l) and, compared to the post-therapeutic TRABs: no statistically significant difference was found at 1 M (8.3±18; P=0.910), statistically significant increase was found at 3 M (14.5±28, P=0.000) and 6 M (17.0±29.0, P=0.001); no statistically significant difference was found at 1 year (P=0.335). A doubling of TRABs in relation to the median pre-therapy value, at some point in the 1st year post-therapy, occurred in 54.7%. These patients had a longer diagnostic-therapeutic interval (3.0±3.0 vs 1.0±2.0 years, P=0.020), higher estimated glandular mass (57.5±32.7 vs 43.0±25, 0 g, P=0.024) and were more frequently of the female gender (60.8 vs 29.4%, P=0.029). There was no significant difference in administered dose (11.0±4.6 vs 10.0±4 mCi, P=0.384). In multivariate analysis, female gender and the estimated glandular mass maintained a statistically significant relationship with the probability of duplication of the TRABs (P=0.015 andP=0.017, respectively).

Discussion: Most patients registered an elevation of the TRABs post-RAI. Female patients with larger glandular mass may be especially at risk for higher elevations. These data may have implications for the extrathyroidal manifestations of Graves’ disease.