ESPE Abstracts

Background: In Autoimmune Thyroid Disease (AITD) two types of TSH receptor antibodies (TSHR-Ab) may be distinguished: thyroid- stimulating immunoglobulin (TSI) that promotes the production of thyroid hormones and thyroid- blocking immunoglobulin (TBI) inhibiting the activity of TSH what leads contrarily to hypothyroidism.

Objective and hypotheses: The aim of this study was to compare mean TSI and TBI levels in large paediatric cohort with AITD and control.

Method: A total of 240 serum samples were obtained from 206 paediatric patients with autoimmune diseases: 33 with Graves’ disease (GD, 28 female, mean age 13.18 years), 69 with Hashimoto’s thyroiditis (HT, 58 female, 13.33 years), 66 with type 1 diabetes (Dt1, 32 female, 13.24 years), 5 with juvenile arthritis (JA, 2 female, 13.8years) and 33 healthy controls (C, 11 female, 11.85 years). A commercial bioassay was used to register TSI level. Results were presented as percentage of specimen-to reference ratio (SRR%, cutoff 140%). TBIs were reported as percentage of inhibition –cutoff 40%.

Results: Of all GD samples, positive values of TSI were detected in 47/53 (88.7%) whereas TBI was negative in 100%. In HT samples TSI and TBI were noted only in 4/83 (4.8%) and in 1/83 (1.2%), respectively. 2/4 (50%) of positive TSI samples were collected from patients with thyroid-associated orbitopathy (TAO). In GD with TAO samples mean TSI levels (SRR% 416.7) were significantly higher in comparison to group without orbitopathy (SRR% 294.3). Difference between those two groups according to TBI levels was unremarkably. In 2/66 (3%) children with Dt1, TSIs were noted (SRR% 459 and 182). All children with JIA and control group were TSHR-Ab negative.

Conclusion: These results indicate strong correlation between TSI and GD. Occurrence of orbitopathy associates with TSI’s presence both in GD and HT. Higher TSI levels in group with vs. without TAO are observed. TBI’s utility seems to be uncertain.