Background: A meta-analysis is needed to comprehensively consolidate findings from the influence of metformin on IGF-1 levels. The present study was conducted with the objective to accurately evaluate the influence of metformin intake on IGF-1 levels via a meta-analysis of randomized controlled trials. Methods: A comprehensive systematic search was carried out in PubMed/MEDLINE, Web of Science, SCOPUS and Embase from inception until June 2019. Weighted mean difference (WMD) with the 95 % CI were applied for estimating the effects of metformin on serum IGF-1 levels. Results: 11 studies involving a total of 569 individuals reported changes in IGF-1 plasma concentrations as an outcome measure. Pooled results demonstrated an overall non-significant decline in IGF-1 following metformin intake (WMD: -8.292 ng/ml, 95 % CI: -20.248, 3.664, p = 0.174) with heterogeneity among (p = 0.000,I2 = 87.1 %). The subgroup analyses displayed that intervention duration <12 weeks on children (WMD:-55.402 ng/ml, 95 % CI: -79.845, -30.960, I2 = 0.0 %) significantly reduced IGF-1. Moreover, in age 18 < years older metformin intake (WMD: 15.125 ng/ml, 95 % CI: 5.522, 24.729, I2 = 92.5 %) significantly increased IGF-1 than 18 ≤ years older (WMD:-1.038 ng/ml, 95 % CI: -3.578,1.502,I2 = 78.0 %). Following dose-response evaluation, metformin intake reduced IGF-1 (coefficient for dose-response analysis= -13.14, P = 0.041 and coefficient for liner analysis= -0.066, P = 0.038) significantly based on treatment duration. Conclusion: We found in children, intervention duration <12 weeks yielded significant reductions in IGF-1, whilst paradoxically, in participants >18 years old, metformin intake significantly increased IGF-1. We suggest that caution be taken when interpreting the findings of this review, particularly given the discordant supplementation practices between children and adults.
Bibliographical noteNOTICE: this is the author’s version of a work that was accepted for publication in Pharmacological Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Pharmacological Research, 151, (2020) DOI: 10.1016/j.phrs.2019.104588
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- Insulin-like growth factor I
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