Benign prostatic hyperplasia (BPH) and related LUTS are common in aging men. Metabolic syndrome (MetS) may influence prostate growth, but evidence on prostate-specific antigen (PSA) and prostate volume (PV) remains conflicting. We aimed to evaluate the association between MetS and objective prostate parameters (PSA and PV) through a systematic review and meta-analysis.

A comprehensive search of PubMed, Scopus, Web of Science, Embase, and Cochrane (inception to 2024) was performed. Cross-sectional studies comparing PSA levels and PV in men with versus without MetS were included. JBI critical appraisal checklist was used for quality assessment. Pooled standardized mean differences (SMD) with 95% confidence intervals were calculated using random-effects models.

From 11,174 initial records, 30 studies (for PSA) and 23 studies (for PV) were included in quantitative synthesis. MetS was associated with a small but statistically significant elevation in PSA levels (SMD = 0.16, 95% CI: 0.03 to 0.29, p = 0.01). A similar significant association was found for prostate volume (SMD = 0.29, 95% CI: 0.12 to 0.46, p < 0.001). Sensitivity analysis restricted to full-text articles confirmed these findings. However, publication bias was detected for PSA (Egger's test p = 0.046; trim-and-fill substantially attenuated the estimate to SMD = 0.036). GRADE certainty was very low for PSA and low for PV.

This meta-analysis demonstrates a modest but statistically significant association between metabolic syndrome (MetS) and both PSA levels and prostate volume (PV). The stronger and more consistent association observed with PV (SMD = 0.29) suggests that MetS may contribute to prostate enlargement, potentially through mechanisms such as chronic inflammation, insulin resistance, and hormonal dysregulation. In contrast, the association with PSA was weaker (SMD = 0.16) and lost significance after adjustment for publication bias, indicating that this finding may be less robust and possibly influenced by selective reporting.

Clinically, these results support the concept that metabolic factors may play a role in prostate growth rather than directly affecting PSA production. The discrepancy between PV and PSA findings may reflect the multifactorial regulation of PSA, which is influenced not only by prostate size but also by inflammation, epithelial activity, and other individual factors.

However, the overall low to very low certainty of evidence, along with the cross-sectional design of included studies, limits causal inference. Therefore, while MetS appears to be associated with larger prostate size, its impact on PSA should be interpreted cautiously. These findings highlight the importance of considering metabolic status in the evaluation of men with LUTS and in the interpretation of PSA levels in clinical practice.

MetS is associated with modestly higher PSA levels and larger prostate volume. While biologically plausible, the PSA finding is vulnerable to publication bias, warranting cautious interpretation. Metabolic status should be considered when interpreting PSA and counseling on prostate growth.