Pericardial effusion as a sign of acquired hypothyroidism in children with Down syndrome.

In three children with Down syndrome and acquired hypothyroidism echocardiography was performed before and after the start of L-thyroxine treatment. Initial studies revealed pericardial effusions which resolved during treatment suggesting that they were caused by hypothyroidism. The incidence of hypothyroidism in Down syndrome is high, but the diagnosis is often missed for lack of specific clinical criteria. The finding of pericardial effusion by echocardiography may be essential in discovering thyroid dysfunction. The cases illustrate that regular thyroid function tests are important in Down syndrome.