A cohort effect on serum testosterone levels in Finnish men.
Level 3 - non-randomized controlled study
Repeated cross-sectional population surveys assessing cohort and secular trends
PubMed 23161753 · doi:10.1530/EJE-12-0288
What was done
Serum levels of total testosterone, gonadotrophins, and sex hormone-binding globulin (SHBG) were measured in 3,271 Finnish men aged 25 to 74 years across three large population surveys conducted in 1972, 1977, and 2002 to determine whether age-independent birth cohort trends exist.
What was found
Serum testosterone decreased cross-sectionally from 25.3 nmol/l in men aged 25–29 years to 16.9 nmol/l in men aged 70–74 years, while SHBG and gonadotrophin levels increased with age. A significant secular birth cohort effect was identified: age-matched men born more recently had lower total testosterone, free testosterone, SHBG, and gonadotrophin levels. In men aged 60–69 years, testosterone declined from 21.9 nmol/l in the 1913–1922 birth cohort to 13.8 nmol/l in the 1942–1951 cohort. These reductions remained statistically significant after adjusting for BMI.
Why it matters
The findings demonstrate that secular declines in testosterone levels extend to Finnish men, a population previously noted for favorable reproductive health metrics, and the concurrent drop in gonadotrophins points to altered hypothalamic-pituitary responsiveness.
Limits
The study is observational and uses repeated cross-sectional surveys rather than longitudinal within-subject tracking. The abstract does not provide exact numerical values or confidence intervals for free testosterone or gonadotrophins, nor does it account for potential confounders beyond BMI, such as comorbidities, environmental exposures, or medication use.
Cited by
- supports Average testosterone levels in men have decreased by up to 20% over the last two decades.