Endocrine Abstracts

Background and Aim: RAIT is successful in achieving cure of thyrotoxicosis. However, 10-15% patients require further doses, usually administered at 4-6 months after the initial dose. We assessed the role of TRAB values in predicting the need for redosing, which could have useful implications.

Patients and Methods: We measured TRAB at diagnosis and at the time of 550MBq RAIT in 54 patients with Graves’ disease. We recorded demographic data and thyroid status at 6, 12, 24 weeks post-RAI, during which antithyroid agents were started as required. Thyroid status at 6 months was correlated to FT3, FT4 and TRAB values.

Results: 71% women, mean age 48 years. 9 (16%) patients were not cured by 6 months. Median (IQR) TRAB at diagnosis and at the time of RAIT were lower in patients cured by RAI compared to patients not cured [3.4 (1.4–9.0) IU/l vs 19.0 (10.6-40.0) IU/l, P=0.001 and 3.3 (1.4–7.5) IU/l vs 7.8 (3.5–29.5) IU/l, P=0.032 respectively]. Similarly, T4 and T3 at the time of diagnosis were lower in patients cured by RAI compared to patients not cured [21.7 (17.0–32.2) vs 40.5 (25.1–50.9) pmol/l, P=0.016 and 9.1 (6.0 – 16.6) vs 37.1 (19.7–46.1) pmol/l, P=0.003, respectively]. Median TRAB, T4 and T3 at diagnosis and pre-RAI TRAb were 5.6, 2.4, 1.9 and 4.1-fold higher, respectively, in patients not cured by RAI compared to patients cured by RAI. TRAB at diagnosis had the maximum area under the ROC curve to identify patients not cured post-RAI.

Conclusions: Initial TRAB measurement at diagnosis of Graves’ thyrotoxicosis and prior to 550MBq RAIT dose can help to identify patients likely to require further RAI doses. Addition of these predictors to the currently established ones can have useful clinical implications.