Background: T3-P-GD, a severe, rare disorder well known in adults, has not previously been described in children. It is characterized by persistently high serum fT3 concentration and normal, or even low, fT4 concentration during drug treatment. This condition is associated with very high titers of TRAb and large goiters, but its pathogenesis remains unclear. The recognition of this form of GD in children is of particular importance, as higher antithyroid drug (ATD) doses are required for its management. We aimed to describe clinical characteristics and management of T3-P-GD in a paediatric population.
Methods: All patients with GD followed for more than 1 year in our department between 2003 and 2013 (n=60) were included, and patients with T3-P-GD (Group I) were defined as high fT3 (>8.0 pmol/l) associated with normal fT4 (<21.5 pmol/l) and undetectable levels of TSH during follow-up, at more than 1 month after ATD treatment initiation.
Results: Eight of the patients with GD had T3-P-GD (13%), at a median of 6.3 (3.39.6) months after diagnosis (n=4) or 2.75 (2.011.9) months after relapse (n=4). At diagnosis, the Group I patients were younger than those of Group II (patients without T3-P-GD) (6.8 (4.311.0) vs 10.7 (7.213.7) years) and had a more severe form of the disease (fT4=92 (6499) vs 63 (4483) pmol/l, fT3=31 (3046) vs 25 (1731) pmol/l; TRAb 40 (3160) vs 17 (825) IU/l) and a lower fT4/fT3 ratio (2.1 (2.02.5) vs 2.7 (2.23.1) for Group I vs II, respectively); P<0.001. FT4/fT3 ratio remained significantly lower for several months. During follow-up, a significantly higher dose of ATD was required (0.63 (0.520.96) vs 0.41 (0.280.56) mg/kg per day after 6 months; P<0.001).
Conclusion: Severe hyperthyroidism and fT4/fT3 ratio at diagnosis may facilitate the identification of patients requiring higher ATD dosage during follow-up.
20 - 22 Sep 2014
European Society for Paediatric Endocrinology