Article Text
Abstract
Background Subclinical hypothyroidism (SCH) has been associated with increased carotid intima-media thickness (C-IMT) in recent studies, but the effects of levothyroxine (L-T4) therapy on C-IMT in SCH patients are still controversial.
Aim To evaluate the effect of L-T4 therapy on endothelial function as determined by C-IMT in patients with SCH.
Methods BeforeJuly 2016, we searched the PubMed, Embase, Cochrane Library and Google Scholar databases, selecting published randomised controlled trials (RCTs) and self-controlled trials for the meta-analysis.
Results Three RCTs with 117 patients were considered appropriate for the meta-analysis. The results of the meta-analysis indicated that L-T4 significantly decreased the development of C-IMT (weighted mean difference (WMD) −0.05 mm, 95% CI −0.08 to –0.01 mm; p=0.025). We also analysed nine studies (self-controlled trials) with 247 patients and extracted the IMT of SCH patients before and after L-T4 treatment. After L-T4 therapy, the pooled estimate of the WMD of decreased C-IMT was −0.04 mm (95% CI −0.07 to –0.02 mm; p=0.05). Subgroup analysis showed that L-T4 therapy was associated with a decrease in C-IMT among patients of mixed genders (WMD −0.03 mm, 95% CI −0.06 to –0.01 mm; p=0.145). L-T4 therapy was associated with a decrease in C-IMT among female patients (WMD −0.07 mm, 95% CI −0.14 to –0.01; p=0.186). Longer treatment (>6 months) also resulted in a significant decrease in C-IMT (WMD −0.05 mm, 95% CI −0.08 to –0.02; p=0.335).
Conclusion This meta-analysis indicates that L-T4 treatment of SCH patients can reduce C-IMT, possibly as a result of the reduction of total cholesterol, triglyceride, low density lipoprotein, systolic blood pressure, diastolic blood pressure, lipoprotein(a), and flow-mediated dilatation. Decreased C-IMT was observed in SCH patients after long-term (>6 months) L-T4 treatment. RCTs with larger samples are needed to verify these observations.
- subclinical hypothyroidism
- carotid intima-media thickness
- thyroxin
- cardiovascular risk
This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Statistics from Altmetric.com
Footnotes
Contributors ZT and CB made search strategies, searched papers from databases, assessed study quality, independently extracted data from the papers and wrote the paper. WH as a third reviewer was asked for advice, if there was disagreement. ZY, WX and ZY participated in the revision of the paper. SZ provided advice on the discussion section of this article.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement No additional unpublished data are available.