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Editor,—The paper by Karlssonet al describes a longitudinal study of monitoring for thyroid disease in children and young people with Down’s syndrome.1 Although the authors conclude that “annual screening is important”, they do not provide any data to justify the interval being a year. We need to know the interval from changes in thyroid stimulating hormone concentrations and autoantibody titres to a subnormal thyroxine level. If the authors have such data, it would be most helpful if they could supply it.
This matter is important in the UK where many districts are introducing an enhanced surveillance programme for children with Down’s syndrome, which includes thyroid function tests. The optimal screening interval for thyroid status is not known and needs to be studied unless Karlssonet al can provide such data.
Drs Annerén and Gustafsson comment:
In the group of Down’s syndrome patients described in our article, 28 of 85 subjects developed hypothyroidism. Half of the subjects acquired the condition before 8 years of age and had no thyroid autoantibodies at the time of diagnosis. Most of those diagnosed after this age displayed such antibodies. However, since these were not analysed until the time of diagnosis there is no information on how long such titres preceded thyroid dysfunction. It is certainly important to measure thyroid autoantibodies annually in patients with Down’s syndrome, especially those older than 8 years of age.
The rationale for annual screening of thyroid stimulating hormone (TSH) is the finding that among our patients with hypothyroidism, four girls (8−17 years) and one boy (10 years) developed significant increases of TSH between two annual controls. However, our experience is that if a child with Down’s syndrome has a normal growth velocity during the preceding year and a TSH concentration well within the normal range at the previous control, hypothyroidism is rarely found.
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