The approach to subclinical thyroid dysfunction

Abstract

Objectives: Subclinical thyroid dysfunction is a prevalent problem. Nonetheless, there are doubts about the best approach.The goal of this revision is systematize this approach based on actual scientific evidence. Methods: A research was made from articles published in Pubmed/Medline, Cochrane Library and Medscape, between 1998 and 2008. From the 226 articles found, 15 were selected, based in clinical interest and type of study. Results: Subclinical thyroid dysfunction includes subclinical hypothyroidism and subclinical hyperthyroidism.The progression to clinical hypothyroidism occurs in 2% to 5% a year. It is more likely when the value of thyroid stimulating hormone (TSH) is elevated and the antiperoxidase antibodies are present. Treatment with thyroxine should be initiated if the level of TSH is superior to10 mU/l.When the level of TSH is between 4,5 mU/l and 10 mU/l, the treatment should be initiated only in symptomatic or pregnant patients.The progression to clinical hyperthyroidism can be 5% a year and is more likely if there is previous thyroid disease or ongoing treatment with amiodarone.The confirmed cases of hyperthyroidism should be sent to an endocrinologist service to determine the aetiology and optimize treatment. The monitorization should be adapted to treatment phase. Conclusions: There is no clear evidence of clinical consequences of non treated subclinical thyroid dysfunction nor benefits of its treatment. Until further studies are available, the best approach should be based on clinical judgement, TSH levels and patients opinion.