Thyroid function tests in adults with Down's syndrome.

Thyroid status was studied in 24 patients above the age of 40 years with Down's syndrome. Three patients had thyroid function tests indicating hypothyroidism. Eight patients had thyroid autoantibodies in serum and 8 patients had a higher than normal level of thyroid stimulating hormone in serum. None of the patients had figures indicating thyrotoxicosis. None of the patients showed any of the clinical signs usually seen in patients with hypothyroidism. It is concluded that biochemical tests indicating hypothyroidism are much more often seen in patients with Down's syndrome than in normal subjects and that thyroid status should be assessed in old patients with this disease.