Introduction: Following treatment of Graves disease (GD), levels of thyrotropin receptor autoantibodies (TRAb) tend to decrease depending on treatment modality and length of follow up. We have assessed TRAb biological activity at follow up, years after GD treatment.
Subjects and methods: TRAb concentration and biological activity were measured in 69 GD patients (59 females; 10 males; median age 59 years; TRAb positive at diagnosis), with follow up ranging from 1 to 13 years. Sera were also tested for TgAb, TPOAb and GADAb.
Results: 31/69 (45%) GD patients remained positive for TRAb one or more years after diagnosis. Fifteen of these were TRAb positive for longer than 5 years after diagnosis. Of the TRAb positive patients 21/31 (68%) were positive for stimulating TRAb (TSAb; range =1553894% stimulation). One TRAb positive patient was positive for blocking type TRAb (TBAb) (42% inhibition). Mean TRAb levels decreased between diagnosis and at follow up irrespective of treatment group (a) Carbimazole (CBZ; n=26) 7.1 U/L vs. 3.1 U/L; (b) radioiodine (RAI; n=26) 11.9 U/L vs 6 U/L; (c) surgery (n=13) 20.7 U/L vs. 2.4 U/l; (all P<0.01). Serum TRAb increased at follow up in 3/26 (CBZ) and 4/26 (RAI) patients. There was good correlation between TRAb and TSAb (
Discussion: In this cohort of GD patients: (a) TRAb concentrations decreased following treatment; (b) some patients remained TRAb positive for 5 or more years after diagnosis; (c) two thirds of TRAb positive subjects had detectable TSAb at follow up (d) some also remained positive for TPOAb and/or TgAb at follow up; and (e) GAD Ab were detectable in 10% at follow up.
|Autoantibodies at follow up||TRAb + ve (n=31)|
|Follow up median (range)||5 years (1-13)|
|TSAb positive||21/31 (68%)|
|TBAb positive||1/31 (3%)|
|TPOAb, TgAb, GADAb positive respectively||25/31, 18/31, 3/31 (81%, 58%, 10%)|