A cohort effect on serum testosterone levels in Finnish men
A Perheentupa1,2, J Ma ¨kinen3, T Laatikainen5, M Vierula1, N E Skakkebaek6, A-M Andersson6and J Toppari1,4
1Department of Physiology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, FI 20520 Turku, Departments of2Obstetrics and
Gynaecology,3Medicine and4Paediatrics, University of Turku, Turku, Finland,5National Institute for Health and Welfare, Mannerheimintie 166, Helsinki
FI 00300, Finland and6Department of Growth and Reproduction, Copenhagen University Hospital, Copenhagen DK-2100, Denmark
(Correspondence should be addressed to A Perheentupa at Department of Physiology, Institute of Biomedicine, University of Turku;
Objective: Toinvestigate whether a population-level decline in serumtestosterone exists in Finnishmen.
In comparison with other European populations, Finnish men have compared well in the studies
of reproductive health (i.e. semen quality, incidence of cryptorchidism and testicular cancer); thus,
we expected no significant cohort-dependent decrease in serum testosterone.
Methods: We analysed serum levels of testosterone, gonadotrophin and sex hormone binding globulin
(SHBG) in 3271 men representing different ages (25–74 years) and birth cohorts within three large
Finnish population surveys conducted in 1972, 1977 and 2002.
Results: Serum testosterone levels decreased (from 25.3 nmol/l in 25- to 29-year-old men gradually to
16.9 nmol/l in 70- to 74-year-old men), whereas SHBG and gonadotrophin levels increased with
increasing age. In addition, a significant secular trend in testosterone (total and free), SHBG and
gonadotrophin levels was observed with lower levels in more recently born age-matched men. Serum
testosterone level decreased in men aged 60–69 years from 21.9 nmol/l (men born 1913–1922) to
13.8 nmol/l (men born 1942–1951). These decreases remained significant following adjustment
for BMI. An age-independent birth cohort effect existed on reproductive hormones measured in the
Finnish men. In concert with the lower free testosterone levels, we observed lower gonadotrophin
levels, suggesting that while 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 testosterone levels than their earlier
born peers. This study offers no explanation for this substantial recent adverse development.
European Journal of Endocrinology 168 227–233
Serum testosterone decreases with age in men, and
longitudinal estimates of this phenomenon are signi-
ficantly greater than cross-sectional estimates (1, 2, 3).
Low serum testosterone has been associated with a
number of compromised health conditions such as
obesity, diabetes, dyslipidemia, decreased bone and
muscle mass and decreased quality of life (4). The
number of elderly men will significantly increase in
the near future and hence their well-being and quality
of life are of general concern for public health. Two
recent studies reported a population-level decline in
serum testosterone in American and Danish men (5, 6).
This would partly explain the observed difference in
age-related serum testosterone decline between cross-
sectional vs longitudinal studies, and it may also reflect
an ongoing adverse trend in male reproductive health.
By contrast, the recent analysis of National Health and
Nutritional Examination Surveys (NHANES) from 1988
to 1991 and from 1999 to 2004 failed to show any
decline in testosterone in USA males (7).
Compared with Danishmen, the Finnish men have
compared well in recent evaluations of reproductive
health (i.e. incidence of cryptorchidism, hypospadias and
testicular cancer and semen quality) (8, 9, 10, 11, 12);
we questioned whether population-level changes in
testosterone levels would also be apparent in Finnish
men and therefore not specific to men from Denmark
and New England.
Subjects and methods
Testosterone, gonadotrophin and sex hormone binding
globulin (SHBG) were analysed in sera of men from
three Finnish population surveys conducted in 1972,
1977 and 2002 by the National Public Health Institute
(presently the National Institute for Health and
Welfare). Data collection and blood sampling were
carried out within the national cardiovascular disease
risk factor surveys named the National FINRISK
European Journal of Endocrinology (2013) 168 227–233 ISSN 0804-4643
q 2013 European Society of EndocrinologyDOI: 10.1530/EJE-12-0288
Online version via www.eje-online.org
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Received 1 April 2012
Revised version received 18 September 2012
Accepted 15 November 2012
Declining testosterone levels in Finnish men
EUROPEAN JOURNAL OF ENDOCRINOLOGY (2013) 168