Does Levothyroxine Improve Exercise Capacity in Patients with Thyroid Disease?

OBJECTIVE: The objective of this selective EBM review is to determine whether or not levothyroxine improves exercise capacity in patients with thyroid disease. SUDY DESIGN: Review of three English language primary studies published in peer-reviewed journals in 2000, 2005, and 2009 DATA SOURCES: Two randomized control trials and one clinical trial comparing leveothyroxine to euthryroid were found using Medline, and PubMed databases. OUTCOMES MEASURED: Each of the three studies measured heart rate and blood pressure before during, and after exercise in patients to determine the effect levothyroxine has on both heart rate and blood pressure RESULTS: One RCT found that submaximal cardiopulmonary exercise performance improved after six months of TSH normalization. The second RCT found that with careful tailoring of TSH-suppressive therapy there is improvement in exercise performance. The controlled clinical trial found that restoring a patient to normal TSH levels does not produce significant changes in substrate response to exercise. CONCLUSIONS: The results demonstrate that the studies do not agree on the effects of levothyroxine or euthyroid on exercise capacity.