Session: SUN 432-458-Thyroid Autoimmunity
Poster Board SUN-439
Methods A total of 100 consecutive untreated hyperthyroid patients with GD (82 female) received antithyroid drugs (ATD) for 24 weeks. Serum TSAb levels were measured at baseline, at 4, 8, 12, 24 and 36 weeks after starting ATD with a FDA-cleared TSH-R bioassay. Response vs. non-response to treatment was defined as biochemical euthyroidism at weeks 24 and 36 vs. persistent hyperthyroidism at week 24 and/or relapse at week 36.
Results In this large prospective trial 89 hyperthyroid patients with GD (71 female, median age 43 years, range 18-74 years, 50 with Graves’ orbitopathy, GO) have completed the 24 week ATD treatment (Methimazole monotherapy 2.5-30 mg/day) and the subsequent 12 week follow up. Of 89 patients, 36 (40%) responded to ATD treatment of whom 17/36 (47%) had GO. In contrast, 53/89 (60%) were non-responders, 33/53 (62%) with GO. Already 12 weeks after starting therapy, marked differences of ATD dose (P < 0.001) and serum TSAb levels (P = 0.002) were noted between responders vs. non-responders. At week 24 and compared with baseline, serum TSAb levels decreased markedly in responders (median SRR% 416 vs. 301, Δ -27.7%, P < 0.001) but increased in non-responders (422 vs. 465, Δ +10.2%, P = 0.082). In contrast, serum levels of TSH-R binding inhibiting immunoglobulins (TBII, automated ECLIA assay) decreased in non-responders at week 24 (14.9 vs. 9.27 IU/L, Δ -37.82%, P = 0.018). TSAb and TBII serum levels positively correlated (r = 0.66, P < 0.001). Median volume of the thyroid gland was 16.3 ml (range 3-36) and 23 ml (5-64) in responders and non-responders, respectively (P = 0.002), whereas a thyroid volume larger than 40 ml was present in non-responders, only. Neither smoking nor gender and age had a significant impact on the outcome.
Conclusions Serum TSAb levels mirror the severity of GD. Their increase during medical treatment is a marker for on-going disease activity. Thus, TSAb levels are a prognostic parameter for GD and reliably predict response to medical therapy.
Disclosure: GJK: Researcher, QUIDEL, CA, USA, Consultant, QUIDEL, CA, USA. Nothing to Disclose: TD, MK, KB, SS
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