Practice Uncertainties Page

Should we treat subclinical hypothyroidism?

BMJ 2008; 337 doi: (Published 16 July 2008) Cite this as: BMJ 2008;337:a834
  1. Cung B Pham, clinical instructor1,
  2. Allen F Shaughnessy, professor1
  1. 1Department of Public Health and Family Medicine, Tufts University School of Medicine, Tufts University Family Medicine Residency at Cambridge Health Alliance, Malden, Massachusetts, USA
  1. Correspondence to: A F Shaughnessy, PharmD, Tufts University Family Medicine Residency, 195 Canal Street, Malden, MA 02148 Allen.Shaughnessy{at}
  • Accepted 2 February 2008

Subclinical hypothyroidism is a laboratory definition: a raised concentration of thyroid stimulating hormone (TSH) yet a normal concentration of free thyroid hormone, without specific symptoms of thyroid dysfunction. Patients with subclinical hypothyroidism have an increased risk of progressing to overt hypothyroidism. Yet uncertainty exists as to the benefits of treating such patients.

What is the evidence of the uncertainty?

Recent systematic reviews of cohort studies have shown a significant increase in coronary heart disease and cardiovascular related mortality in people with subclinical hypothyroidism and a TSH concentration >10 mU/l, but no difference in overall mortality.1 2 The benefits of treating subclinical hypothyroidism are also uncertain: although two systematic reviews have suggested that treatment may decrease total cholesterol and low density lipoprotein cholesterol levels, particularly in people with TSH concentrations of >10 mU/l,3 4 no research has shown a decrease in coronary heart disease or mortality with treatment.

The Clinical Evidence review reports mixed results from small …

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