Randomised Trial of Block and Replace versus dose titration antithyroid drug treatment in children and adolescents with thyrotoxicosis.

<strong>This dataset contains the study regimens for the randomised controlled trial. </strong> <strong>Context</strong> First line treatment of thyrotoxicosis in young people is thionamide antithyroid drug (ATD) in a blocking dose with levothyroxine replacement (block and replace, BR) or in a smaller dose tailored to render the patient euthyroid (dose titration, DT). <strong>Objective</strong> To determine which regimen provides more stable biochemical control. <strong>Design and setting</strong> A multi-centre phase III, open-label randomised trial comparing BR with DT in patients aged 2 to 16 years with newly diagnosed thyrotoxicosis at 15 UK centres. Patients were randomised shortly after diagnosis and treated for 3 years. The primary outcome was the percentage of serum thyroid stimulating hormone (TSH) levels in the reference range between 6 months and 3 years. Secondary outcomes included the proportion of Free thyroxine (FT4) levels in the reference range, adverse event frequency and 4y outcome (remission/relapse). <strong>Results</strong> Eighty-two patients were randomised, with details on clinical course in 81 (62 Female); 40 were allocated to BR (41 DT). Three withdrew with one ineligible. The mean percentage of serum TSH within reference range was 60·2% in BR and 63·8% in DT patients; adjusted difference 4·3%, 95% CI (-7·8 to 16·4);p=0.48. Proportions for FT4 were 79·2% in BR and 85·7% in DT patients; adjusted difference 6·8%, (-0·2 to 15·6);p=0·13. Three patients developed neutropenia – all on BR. 6 BR and 10 DT patients were in remission at 4y. <strong>Conclusion</strong> This trial has shown no evidence to suggest that BR improves biochemical stability. DT, recommended by American Thyroid Association guidelines, remains the preferred approach in this age group.