ESPE Abstracts

Background: Ireland has the highest prevalence of Down syndrome (DS) in Europe, affecting ~1 in 500 live births. Patients with DS are at increased risk of developing thyroid disorders during childhood. Hyperthyroidism can be difficult to recognise and treat in this population. First-line therapy with anti-thyroid drugs (ATDs) may help achieve remission, but relapse is common following discontinuation of medication. Definitive treatment with radio ablation or surgery is often considered but may have additional risks in the DS population.

Objective: We report a case series of infants with DS who developed hyperthyroidism and were treated with successfully anti-thyroid drugs.

Methods: Five children with DS had hyperthyroidism confirmed at our centre. Information regarding clinical features at presentation, diagnostic testing and management was recorded.

Results: Thyrotoxicosis was confirmed in five children (two females and three males) at a mean age of 5.5 years (range 3.7–8.0 years). Behaviour disturbance and disordered sleep were the presenting symptoms in 4/5. Diagnostic testing confirmed an increased thyroxine level (T₄, mean 36.4 pmol/l, range 25.9–49.4 pmol/l), suppressed TSH level (<0.01 mIU/l) and TSH receptor antibody (TRAb) positivity (TRAb, mean 92.0 U/l, range 6.4–400 U/l). All children were treated with ATDs with a mean duration of 2.6 years (range 0.25–4 years). After 24 months of therapy, consideration was given to a trial off treatment for four of five children but all became clinically or biochemically hyperthyroid when ATD dose was reduced. All children currently remain clinically and biochemically euthyroid on ATDs and none have proceeded to definitive therapy. ATDs were well tolerated in our cohort, with no serious side effects noted.

Conclusion: Anti-thyroid drugs should be considered a safe and effective option for long-term management of hyperthyroidism in the DS population and may be preferable to more definitive treatments.