A Cohort Effect on Serum Testosterone Levels in Finnish Men.

A Perheentupa, Department of Physiology, Institute of Biomedicine, University of Turku, Turku, Finland.
European Journal of Endocrinology (Impact Factor: 3.69). 11/2012; 168(2). DOI: 10.1530/EJE-12-0288
Source: PubMed

ABSTRACT OBJECTIVE: To investigate whether a population-level decline in serum testosterone (T) exists in Finnish men. In comparison to other European populations, Finnish men have compared well in studies of reproductive health (i.e. semen quality, incidence of cryptorchidism and testicular cancer), thus we expected no significant cohort dependent decrease in serum T. METHODS: we analysed serum levels of T, gonadotrophin and sex hormone binding globulin (SHBG) in 3271 men representing different ages (25-74 y) and birth cohorts within three large Finnish population surveys conducted in 1972, 1977 and 2002. RESULTS: Serum T levels decreased (from 25.3 nmol/l in 25-29 year old men gradually to 16.9 nmol/l in 70-74 year old men), whereas SHBG and gonadotrophin levels increased with increasing age. In addition, a significant secular trend in T (total and free), SHBG and gonadotrophin levels was observed with lower levels in more recently born age-matched men. Serum T decreased in men aged 60-69 years from 21.9 nmol/l (men born 1913-1922) to 13.8 nmol/l (men born 1942-51). These decreases remained significant following adjustment for body mass index. An age-independent birth cohort effect existed on reproductive hormones measured in the Finnish men. In concert with the lower fT levels we observed lower gonadotrophin levels, suggesting that whilst there may be detrimental changes at the gonad level, the hypothalamus-pituitary -axis is not responding appropriately to this change. CONCLUSIONS: The more recently born Finnish men have lower T levels than their earlier born peers. This study offers no explanation for this substantial recent adverse development.

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