New research by Romani et al. from The John Hopkins University in Baltimore has been published in The Knee and has shown that testosterone levels can have an impact on the strength of the anterior cruciate ligament (ACL). Romani’s previous research has shown that estrogen could reduce ACL strength.
The most recent study was performed on male rats. The ACLs of normal rats were compared to those of castrated rats. The testosterone levels in the castrated rats was close to zero. The researchers concluded that “rats with normal circulating testosterone had higher ACL load-to-failure and ultimate stress, indicating that testosterone may influence ACL strength and the injury rate of the ligament“. The results suggest that testosterone may help to strengthen the ACL. If coupled with the findings that estrogen could weaken the ACL, we can start to understand some of the reasons behind the differences in prevalence of ACL injuries between the sexes. Obviously, this only holds if these findings are the same in humans as well. It would also be interesting to know if these findings apply to other ligaments.
A recent study by Rubinstein et al. published in The Clinical Journal of Pain has shown that long-term use of opioid painkillers by men is associated with lower levels of testosterone. This effect is much more prevalent when using long-acting opioids. Low testosterone or hypogonadism, as it’s also known, has been linked with decreases in muscle mass, bone density, cognition, mood, sex drive and general quality of life.
A study by Arthur English and Nancy Thompson has found that exercise can promote the regeneration of peripheral nerve injuries. In both males and females, the effect requires the assistance of androgens such as testosterone.