Abstract
Previous studies were controversial in the effects of metabolic syndrome (MetS) on semen quality and circulating sex hormones, and thus we conducted a systematic review and meta-analysis to clarify the association. A systematic search was conducted in public databases to identify all relevant studies, and study-specific standardized mean differences (SMD) and 95% confidence intervals (CI) were pooled using a random-effects model. Finally, 11 studies were identified with a total of 1,731 MetS cases and 11,740 controls. Compared with the controls, MetS cases had a statistically significant decrease of sperm total count (SMD: −0.96, 95% CI: −1.58 to −0.31), sperm concentration (SMD: −1.13, 95% CI: −1.85 to −0.41), sperm normal morphology (SMD: −0.61, 95% CI: −1.01 to −0.21), sperm progressive motility (SMD: −0.58, 95% CI: −1.00 to −0.17), sperm vitality (SMD: −0.83, 95% CI: −1.11 to −0.54), circulating follicle-stimulating hormone (SMD: −0.87, 95% CI: −1.53 to −0.21), testosterone (SMD: −5.61, 95% CI: −10.90 to −0.31), and inhibin B (SMD: −2.42, 95% CI: −4.52 to −0.32), and a statistically significant increase of sperm DNA fragmentation (SMD: 0.76, 95% CI: 0.45 to 1.06) and mitochondrial membrane potential (SMD: 0.89, 95% CI: 0.49 to 1.28). No significant difference was found in semen volume, sperm total motility, circulating luteinizing hormone (LH), estradiol, prolactin and anti-Müllerian hormone (AMH) (P > 0.05). In conclusion, this meta-analysis demonstrated the effects of MetS on almost all the semen parameters and part of the circulating sex hormones, and MetS tended to be a risk factor for male infertility. Further larger-scale prospective designed studies were needed to confirm our findings.
Highlights
Metabolic syndrome (MetS) is a complex of clinical conditions characterized by abdominal obesity, dyslipidemia, hypertension and insulin resistance [1, 2]
As a collection of these features, MetS was thought to be involved in the pathogenesis of male infertility
According to the World Health Organization (WHO), infertility had an incidence of 8∼12% in childbearing couples worldwide, among which male infertility accounted for 40∼50% [27]
Summary
Metabolic syndrome (MetS) is a complex of clinical conditions characterized by abdominal obesity, dyslipidemia, hypertension and insulin resistance [1, 2]. The meta-analysis by Brand et al [11] indicated a lower level of testosterone in men with MetS, but it failed to evaluate the effects of MetS on other circulating sex hormones and semen quality. No metaanalyses have systematically and quantitatively evaluated the effects of MetS on both semen quality and several sex hormones in men, there existed obvious controversies in original studies. This meta-analysis aimed to clarify the role of MetS in male infertility by assessing its impact on both semen and hormonal parameters
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