Functional TSH receptor antibodies in children with autoimmune thyroid diseases.

Introduction: The diagnostic value of the level of TSH receptor antibodies (TSHR-Ab) in the population of children with autoimmune thyroid diseases (AITDs) is still unknown. The aim of this cross-sectional study was to investigate the prevalence of TSHR-Ab in a paediatric cohort with AITD and healthy controls.

Materials And Methods: A total of 240 serum samples were obtained from 205 patients with AITD, type 1 diabetes (T1D), juvenile arthritis (JA), and healthy controls (C). TSHR stimulating (TSI) and -blocking (TBI) immunoglobulins were measured in cell-based bioassays using CHO cells expressing a chimeric TSHR and a c-AMP response-element-dependent luciferase. TSI was reported as percentage of specimen-to-reference ratio (cutoff 140SRR%). Blocking activity was defined as percent inhibition of luciferase expression relative to induction with bovine TSH alone (40% inhibition).

Results: C as well as children with JA and T1D were both TSI and TBI negative. In contrast, children with Graves' disease (GD) were positive for TSI in 47/53 samples (88.7%) while those with thyroidal and orbital GD showed TSI positivity in 95.8% (23/24 samples). Serum TSI levels were SRR% 320 ± 157 and 417 ± 135 in GD and GD + orbitopathy, respectively (p = .02). Children with Hashimoto's thyroiditis (HT) were TSI positive in 4/83 (4.8%) samples, including two with orbital involvement. TSI levels were increased in HT children with vs. those without eye disease (SRR% 177 vs. 51, p < .01). In comparison, TBI were negative in all tested samples of children with GD but positive in one HT sample.

Conclusions: In conclusion, TSI is prevalent in children with GD while the highest serum TSI levels were noted in children with AITD and orbitopathy.