Effects of testosterone treatment on glucose metabolism and symptoms in men with type 2 diabetes and the metabolic syndrome: a systematic review and meta-analysis of randomized controlled clinical trials.

Context: The effects of testosterone treatment on glucose metabolism and other outcomes in men with type 2 diabetes (T2D) and/or the metabolic syndrome are controversial.

Objective: To perform a systematic review and meta-analysis of placebo-controlled double-blind randomized controlled clinical trials (RCT) of testosterone treatment in men with T2D and/or the metabolic syndrome.

Data Sources: A systematic search of RCTs was conducted using Medline, Embase and the Cochrane Register of controlled trials from inception to July 2014 followed by a manual review of the literature.

Study Selection: Eligible studies were published placebo-controlled double-blind RCTs published in English.

Data Extraction: Two reviewers independently selected studies, determined study quality and extracted outcome and descriptive data.

Data Synthesis: Of the 112 identified studies, seven RCTs including 833 men were eligible for the meta-analysis. In studies using a simple linear equation to calculate the homeostatic model assessment of insulin resistance (HOMA1), testosterone treatment modestly improved insulin resistance, compared to placebo, pooled mean difference (MD) -1·58 [-2·25, -0·91], P < 0·001. The treatment effect was nonsignificant for RCTs using a more stringent computer-based equation (HOMA2), MD -0·19 [-0·86, 0·49], P = 0·58). Testosterone treatment did not improve glycaemic (HbA1c) control, MD -0·15 [-0·39, 0·10], P = 0·25, or constitutional symptoms, Aging Male Symptom score, MD -2·49 [-5·81, 0·83], P = 0·14).

Conclusions: This meta-analysis does not support the routine use of testosterone treatment in men with T2D and/or the metabolic syndrome without classical hypogonadism. Additional studies are needed to determine whether hormonal interventions are warranted in selected men with T2D and/or the metabolic syndrome.