Effect of L-thyroxine treatment versus a placebo on serum lipid levels in patients with sub-clinical hypothyroidism.

Sub-clinical hypothyroidism is a common disease and whether L-thyroxine replacement treatment improves serum lipid levels in affected patients remains controversial. Thus, the aim of the present meta-analysis was to assess the effect of L-thyroxine therapy on serum lipid levels in sub-clinical hyperthyroidism. Relevant randomized controlled trials (RCTs) containing continuous data, published until July 2015 were retrieved from the Cochrane Library, PubMed, Medline, Google Scholar and Embase databases and subjected to meta-analysis using Review Manager software version 5.2 (The Nordic Cochrane Centre, Copenhagen, Denmark). Seven RCTs comprising 319 patients were included. The overall methodological quality of the RCTs was good. Statistical analysis revealed that serum low-density lipoprotein-cholesterol (LDL-C) levels were significantly decreased after L-thyroxine treatment [mean difference (MD): -0.23; 95% confidence interval: -0.44, -0.03; P=0.02], while changes of total cholesterol (TC), triglyceride (TG) and high-density lipoprotein-cholesterol (HDL-C) were not significant (MD: -0.18, P=0.09; MD: -0.02, P=0.78; and MD: -0.06, P=0.14, respectively). In conclusion, the meta-analysis performed in the present study revealed that compared with placebo treatment, L-thyroxine significantly improved serum LDL-C levels in patients with sub-clinical hypothyroidism, while not significantly affecting TC, TG and HDL-C levels.