Triiodothyronine-predominant Graves' disease in childhood: detection and therapeutic implications

Abstract

Objective: To assess in a pediatric population, the clinical characteristics and management of triiodothyronine-predominant Graves' disease (T3-P-GD), a rare condition well known in adults, but not previously described in children.

Design: We conducted a university hospital-based observational study.

Methods: All patients with GD followed for more than 1 year between 2003 and 2013 (n=60) were included. T3-P-GD (group I) was defined as high free T3 (fT3) concentration (>8.0 pmol/l) associated with a normal free thyroxine (fT4) concentration and undetectable TSH more than 1 month after the initiation of antithyroid drug (ATD) treatment. Group II contained patients with classical GD without T3-P-GD.

Results: Eight (13%) of the patients were found to have T3-P-GD, a median of 6.3 (3.0-10.5) months after initial diagnosis (n=4) or 2.8 (2.0-11.9) months after the first relapse after treatment discontinuation (n=4). At GD diagnosis, group I patients were more likely to be younger (6.8 (4.3-11.0) vs 10.7 (7.2-13.7) years) and had more severe disease than group II patients, with higher serum TSH receptor autoantibodies (TRAb) levels: 40 (31-69) vs 17 (8-25) IU/l, P<0.04, and with slightly higher serum fT4 (92 (64-99) vs 63 (44-83) pmol/l) and fT3 (31 (30-46) vs 25 (17-31) pmol/l) concentrations. During the 3 years following T3-P-GD diagnosis, a double dose of ATD was required and median serum fT4:fT3 ratio remained lower in group I than in group II.

Conclusion: Severe hyperthyroidism, with particularly high TRAb concentrations at diagnosis, may facilitate the identification of patients requiring regular serum fT3 determinations and potentially needing higher doses of ATD dosage during follow-up.