TSH receptor antibody levels (TSHAb) in hyperthyroid patients with Graves disease (GD): an evaluation of the outcome of 131I therapy
Jolanta Kijek1, Jerzy S Tarach2, Maria Kurowska2, Bożena Szymanek1, Beata Chrapko1 & Anna Dabrowska2
Aim: The aim of the study was to evaluate the relationship between TSHAb levels and thyroid function and size in patients with Graves disease and then to estimate the influence of TSHAb on the outcome of 131I therapy.
Material and methods: Two hundred and one patients (168 females and 33 males, mean age 47.76 years, range 1884) with Graves disease were enrolled. Before therapy, plasma fT3, fT4, TSH (DELFIA technique) and TSHAb (radioreceptor method) were measured in all patients. A thyroid technetium-99m scan was performed and iodine uptake (RIU) was measured after 24 and 48 h, then effective half-life (EHL-RIU) was determined. The therapeutic activity of 131I was calculated by Marinellis formula. During the one-year follow-up thyroid function was assessed.
Results: The levels of TSHAb ranged from 1.1 to 405 U/l (mean 56.98±86.95) before therapy. One year after 131I therapy 69 patients were hypothyroid (HP), 56 were euthyroid (E), and 76 were hyperthyroid (H). In the 126 effectively treated patients (E and HP), TSHAb concentration was 23.4 U/l±27.66, and in the 76 ineffectively treated patients it was 71.4 U/l±97.46. A comparison of mean values showed a statistically significant difference (P=0.0001). A statistical analysis also showed that there was a statistically significant relationship between TSHAb and thyroid mass (P=0.0001) as well as EHL-RIU (P=0.002).
Conclusions: There is a relationship between TSHAb concentration and thyroid size as well as effective half-life. In patients ineffectively treated with 131I therapy TSHAb concentration was higher than in those treated effectively.