Lack of evidence to support treatment decisions for subclinical hypothyroidism

Clinical question: 
Should thyroxine replacement be prescribed for patients with subclinical hypothyroidism?
Bottom line: 
Trials comparing thyroxine replacement for subclinical hypothyroidism with placebo or no treatment showed no difference in survival or decreased cardiovascular morbidity. Data on health-related quality of life and symptoms did not demonstrate significant differences between intervention groups. Some evidence indicates thyroxine replacement improves some parameters of lipid profiles and left ventricular function. Clinical judgement and patient preference is still best when deciding treatment for subclinical hypothyroidism.
Caveat: 
Many studies had participants with prior thyroid dysfunction and the studies were small with limited follow-up. Only 2 population-based studies were included. Other studies were in outpatient clinic populations. All bar 3 studies had a mean patient age of 35 years.
Context: 
The introduction of sensitive assays to determine thyroid stimulating hormone (TSH) concentrations has increased the number of newly diagnosed cases of subclinical hypothyroidism. Subclinical hypothyroid disease is the most common condition found during thyroid function screening.
Review CD#: 
CD003419
PEARLS No: 
103
Date: 
October, 2008
Authored by: 
Brian R McAvoy