# β-Hydroxy-β-methyl butyrate (HMB) supplementation elevates testosterone levels without significant changes to cortisol, IGF-1, or growth hormone in adults: a GRADE-assessed systematic review and meta-analysis of controlled trials

## TL;DR

HMB supplementation increases testosterone in adults but does not significantly affect cortisol, IGF-1, or growth hormone.

## Contribution

This is the first GRADE-assessed systematic review and meta-analysis on HMB's hormonal effects in adults.

## Key findings

- HMB significantly increased testosterone levels (SMD: 0.82).
- No significant changes were observed in cortisol, IGF-1, or GH levels.
- The quality of evidence ranged from low to high according to GRADE criteria.

## Abstract

Increasing interest in improving physical performance and muscle mass in adults has highlighted the potential benefits of β-hydroxy-β-methyl butyrate (HMB) supplementation. While numerous studies have been conducted in this area, the hormonal response to HMB remains unclear. We hypothesized that HMB supplementation would significantly increase anabolic hormone levels, particularly testosterone, while not affecting the cortisol, IGF-1, or growth hormone levels in adults.

A comprehensive search of databases, including PubMed, Web of Science, and Scopus, was performed to identify relevant studies until January 2024. The protocol was registered with Prospero (CRD42024552074). The studies evaluated the impact of HMB supplementation on hormonal outcomes, including testosterone, cortisol, insulin-like growth factor-1 (IGF-1), and growth hormone (GH). Utilizing a random-effects model, the standardized mean differences (SMDs) and their corresponding 95% confidence intervals (CIs) were computed, and the GRADE framework was applied.

A total of 15 controlled trials (CTs) comprising 712 participants were included. HMB supplementation significantly increased testosterone levels (SMD: 0.82, 95% CI: 0.35, 1.29, p = 0.001). However, no significant changes were observed in the cortisol (SMD: −0.39, 95% CI: −0.92, 0.14, p = 0.14), IGF-1 (SMD: −0.18, 95% CI: −0.54, 0.18, p = 0.33), and GH (SMD: 0.04, 95% CI: −0.73, 0.82, p = 0.91) levels. According to the GRADE criteria, the quality of evidence was rated as ranging from low to high.

HMB supplementation significantly elevates testosterone levels in adults without distinct impacts on other hormonal pathways. However, it does not appear to significantly influence the cortisol, IGF-1, or GH levels.