Sir.—The RADIOLOGICAL CASE OF THE MONTH in the June 1987 issue of AJDC1 concerned a 9-year-old girl with Down's syndrome with cardiac tamponade secondary to hypothyroidism. The authors suggested that early recognition of hypothyroidism was difficult because of the features of Down's syndrome, and, therefore, they favored the development of unrecognized hypothyroidism and massive pericardial fusion.
Unfortunately, the authors' observation is probably true, but this condition might have been avoided if preventive steps had been taken for a condition relatively common in patients with Down's syndrome. The prevalence of hypothyroidism in adults with Down's syndrome has been reported in different studies to range from 13% to 54%. A recent report placed the incidence of hypothyroidism in children at approximately 10%.2 It is unclear how often thyroid tests should be performed, but many authorities suggest annual testing. Some also recommend testing every six months for the first two years.