Factors Associated With Circulating Sex Hormones in Men : Individual Participant Data Meta-analyses

Area of Science:

• Endocrinology
• Men's Health
• Reproductive Health

Background:

• Circulating testosterone levels in men are influenced by various factors, complicating the interpretation of measurements.
• Understanding these modulating factors is crucial for accurate clinical assessment.

Purpose of the Study:

• To identify and clarify the sociodemographic, lifestyle, and health-related factors associated with variations in male sex hormone concentrations.
• To provide a comprehensive analysis of factors affecting total testosterone, SHBG, and LH levels.

Main Methods:

• Systematic literature searches were conducted up to July 2019.
• Individual participant data from 9 prospective cohort studies (n=21,074) and aggregate data from 2 studies (n=4,075) were analyzed.
• Two-stage random-effects meta-analyses were performed on sociodemographic, lifestyle, and health factors in relation to hormone concentrations.

Main Results:

• Testosterone shows a nonlinear association with age, with levels stable until 70 years and declining thereafter.
• Higher body mass index (BMI), marriage, reduced vigorous physical activity, former smoking, hypertension, cardiovascular disease, cancer, and diabetes were all associated with lower testosterone concentrations.
• Sex hormone-binding globulin (SHBG) was directly associated with age and inversely with BMI, while luteinizing hormone (LH) increased with age in men over 70.

Conclusions:

• Multiple factors, including age (especially >70 years), obesity, diabetes, and cancer, are significantly associated with variations in male testosterone, SHBG, and LH concentrations.
• Reduced testosterone and increased LH post-70 may indicate impaired testicular function.
• Accurate interpretation of testosterone measurements requires consideration of these key influencing factors.