Functional TSH receptor antibodies in children with autoimmune thyroid diseases

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.

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).

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.

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