Background: The natural history of thyroid function in adults with Down syndrome (DS) is unknown.
Method: This study investigated annual thyroid function tests in 200 adults with DS over a 10-year period.
Results: Transient and persistent thyroid dysfunction was common. The 5- and 10-year incidence of definite hypothyroidism was 0.9%-1.64% and 13.6%, respectively. Subclinical hypothyroidism was not found to be an early sign for definite hypothyroidism.
Conclusions: Routine screening for adults with DS who are euthyroid can be reduced to every 5 years rather than the present policy of every 1-2 years.