Summary: There are many threats revealed by science. We obsess about some, such as climate change. Others we ignore, such as falling testosterone levels in men. This loss of our manliness might explain many things. America’s falling crime rates? The increased frequency of women filing for divorce (why hang around with a low-T beta?). Perhaps even our defeats in Iraq and Afghanistan, and the contempt of migrants for our borders.
CNN reports the news, with mockery: “Modern life rough on men“, 18 August 2011 — Opening…
“Didn’t men use to be more masculine? They were more ready to fight back, right? They walked with more swagger, and just did more things their way. Researchers can’t measure swagger – but they can measure testosterone, the male sex hormone most responsible for masculine behaviors – and studies show that testosterone levels in men have been on the decline for decades.
Two major studies have confirmed the phenomenon, one in U.S. men and another in Danish men. In the U.S. study, the total testosterone levels measured in men’s blood dropped approximately 22% between 1987 and 2004.
Of course testosterone levels drop as men get older, but what makes the study shocking is that men today actually have less testosterone than men used to have at the same age. The challenges to men’s health may not be limited to testosterone levels. The amount of sperm in ejaculated semen may be falling too. …”
There are other dimensions to the problem: “Why are men’s sperm rates falling?” by Dr. Phil Hammond in The Telegraph, 17 March 2014 — “Men’s sperm production is decreasing rapidly and the scientific community is struggling to find an explanation.”
Something is happening. Thousands of papers in the past few years examine the dynamics and effects of this powerful hormone. It responds to changes in a person’s social and physical environment. It influences men’s health and behavior in many ways.
Below the fold are summaries of eight papers, among the few that examine the changes during the past few decades in testosterone levels and male fertility. These longitudinal studies are of great value — but complex and expensive — and hence rare. They have been ignored by policy makers, but deserve attention. Lead poisoning helped bring down the Roman Empire. It was one of many factors in its decline, but one that they were unable to see (they knew about the danger of lead pipes, but not other sources of lead poisoning).
Research about changes in men’s testosterone levels
These studies paint a confusing picture. The research strongly suggests that something is happening, but its magnitude and causes remain unknown. Red emphasis added.
(1) “Evidence For Decreasing Quality Of Semen During Past 50 Years” by Elisabeth Carlsen et al, British Medical Journal, 12 September 1992 — Abstract…
“Objective: To investigate whether semen quality has changed during the past 50 years.
“Design: Review of publications on semen quality in men without a history of infertility selected by means of Cumulated Index Medicus and Current List (1930-1965) and MEDLINE Silver Platter database (1966-August 1991).
“Subjects: 14,947 men included in a total of 61 papers published between 1938 and 1991.
“Main outcome measures: Mean sperm density and mean seminal volume.
“Results: Linear regression of data weighted by number of men in each study showed a significant decrease in mean sperm count from 113 x 10(6)/ml in 1940 to 66 x 10(6)/ml in 1990 (p < 0.0001) and in seminal volume from 3.40 ml to 2.75 ml (p = 0.027), indicating an even more pronounced decrease in sperm production than expressed by the decline in sperm density.
“Conclusions: There has been a genuine decline in semen quality over the past 50 years. As male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility. The biological significance of these changes is emphasised {sic} by a concomitant increase in the incidence of genitourinary abnormalities such as testicular cancer and possibly also cryptorchidism and hypospadias, suggesting a growing impact of factors with serious effects on male gonadal function.”
(2) “Secular variations in sperm quality: fact or science fiction?” by Luc Multigner in Reports in Public Health, March/April 2002.
“The debate concerning the possible degradation in human sperm quality began in the 1970s, was revived at the beginning of the 1990s and has continued to mobilize the scientific community ever since. After the meta-analysis by Carlsen et al. (1992) showing a decline in human semen quality over the last 50 years, several groups investigated the sperm characteristics of more or less homogeneous groups of men who had provided semen at the same center for 10 to 20 years.
“A significant decrease in sperm concentration was reported in some studies, but not in others. Meanwhile, there is an increasing number of reports suggesting that physical and chemical factors introduced and spread by human activity in the environment may have contributed to sperm decline. At the end of the 20th century the debate on declining semen quality is not closed. The lack of certainty and the serious consequences that such a decline would have on the fertility of human populations make this an important public health issue at the start of the 21st century. For this reason, intensive research should be developed in both fundamental and epidemiological domains, particularly in South America, where industrial and agricultural pollution pose a serious threat to the population.”
(3) “Measuring male infertility: epidemiological aspects” by Fábio Firmbach Pasqualotto et al, in the Revista do Hospital das Clínicas, 2003 (3) — Abstract…
“Evidence suggests that human semen quality may have been deteriorating in recent years. Most of the evidence is retrospective, based on analysis of data sets collected for other purposes. Measures of male infertility are needed if we want to monitor the biological capacity for males to reproduce over time or between different populations. We also need these measures in analytical epidemiology if we want to identify risk indicators, risk factors, or even causes of an impaired male fecundity that is, the male component in the biological ability to reproduce.
“The most direct evaluation of fecundity is to measure the time it takes to conceive. Since the time of conception may be missed in the case of an early abortion, time to get pregnant is often measured as the time it takes to obtain a conception that survives until a clinically recognized pregnancy or even a pregnancy that ends with a live born child occurs. A prolonged time required to produce pregnancy may therefore be due to a failure to conceive or a failure to maintain a pregnancy until clinical recognition.
Studies that focus on quantitative changes in fecundity (that does not cause sterility) should in principle be possible in a pregnancy sample. The most important limitation in fertility studies is that the design requires equal persistency in trying to become pregnant and rather similar fertility desires and family planning methods in the groups to be compared. This design is probably achievable in exposure studies that make comparisons with reasonable comparable groups concerning social conditions and use of contraceptive methods.”
(4) “Is human fecundity declining?” by Niels E. Skakkebæk et al, in the International Journal of Andrology, February 2006 — Gated. Abstract…
“The decreasing trends in fertility rates in many industrialized countries are now so dramatic that they deserve much more scientific attention. Although social and behavioural factors undoubtedly play a major role for these trends, it seems premature, and not based on solid information, to conclude that these trends can be ascribed to social and behavioural changes alone. There is evidence to suspect that changing lifestyle and increasing environmental exposures, e.g. to endocrine disrupters, are behind the trends in occurrence of male reproductive health problems, including testis cancer, undescended testis and poor semen quality. These biological factors may also contribute to the extremely low fertility rates.
“However, the necessary research is complex and requires non-traditional collaboration between demographers, epidemiologists, clinicians, biologists, wild life researchers, geneticists and molecular biologists. This research effort can hardly be carried out without major support from governments and granting agencies making it possible to fund collaborative projects within novel research networks of scientists.”
(5) Press release: “Testosterone Levels in Men Decline Over Past Two Decades, Study Shows“. Study: “A Population-Level Decline in Serum Testosterone Levels in American Men” by Thomas G. Travison et al, in the Journal of Clinical Endocrinology and Metabolism, October 2007.
“Age-specific estimates of mean testosterone (T) concentrations appear to vary by year of observation and by birth cohort, and estimates of longitudinal declines in T typically outstrip cross-sectional decreases. These observations motivate a hypothesis of a population-level decrease in T over calendar time, independent of chronological aging.
“The goal of this study was to establish the magnitude of population-level changes in serum T concentrations and the degree to which they are explained by secular changes in relative weight and other factors. We describe a prospective cohort study of health and endocrine functioning in randomly selected men of age 45–79 yr. We provide three data collection waves: baseline (T1: 1987–1999) and two follow-ups (T2: 1995–1997, T3: 2002–2004).
“This was an observational study of randomly selected men residing in greater Boston, Massachusetts. Data obtained from 1374, 906, and 489 men at T1, T2, and T3, respectively, totaling 2769 observations taken on 1532 men. The main outcome measures were serum total T and calculated bioavailable T.
“We observe a substantial age-independent decline in T that does not appear to be attributable to observed changes in explanatory factors, including health and lifestyle characteristics such as smoking and obesity. The estimated population-level declines are greater in magnitude than the cross-sectional declines in T typically associated with age.
“These results indicate that recent years have seen a substantial, and as yet unrecognized, age-independent population-level decrease in T in American men, potentially attributable to birth cohort differences or to health or environmental effects not captured in observed data.“
(6) “Secular decline in male testosterone and sex hormone binding globulin serum levels in Danish population surveys” by Anna-Marie Andersson et al, in The Journal of Clinical Endocrinology & Metabolism, 1 December 2007 — Abstract…
“Adverse secular trends in male reproductive health have been reported to be reflected in increased testicular cancer risk and decreased semen quality in more recently born men. These secular trends may also be reflected by changes in Leydig cell function. The objective of the study was to examine whether an age-independent time trend in male serum testosterone levels exists.
“Testosterone and SHBG were analyzed in 5350 male serum samples from four large Danish population surveys conducted in 1982-1983, 1986-1987, 1991-1992, and 1999-2001. Free testosterone levels were calculated. The effects of age, year of birth, and time period on hormone levels were estimated in a general linear statistical model.
“Testosterone, SHBG, and calculated free testosterone levels in Danish men in relation to age, study period, and year of birth were measured. Serum testosterone levels decreased and SHBG levels increased with increasing age. In addition to this expected age effect, significant secular trends in testosterone and SHBG serum levels were observed in age-matched men with lower levels in the more recently born/studied men. No significant age-independent effect was observed for free testosterone. Adjustment for a concurrent secular increase in body mass index reduced the observed cohort/period-related changes in testosterone, which no longer were significant. The observed cohort/period-related changes in SHBG levels remained significant after adjustment for body mass index.
“The observed age-independent changes in SHBG and testosterone may be explained by an initial change in SHBG levels, which subsequently lead to adjustment of testosterone at a lower level to sustain free testosterone levels.”
(7) “Is human fecundity declining in Western countries?” by Egbert te Velde et al, in Human Reproduction, June 2010 — Abstract…
“Since Carlsen and co-workers reported in 1992 that sperm counts have decreased during the second half of the last century in Western societies, there has been widespread anxiety about the adverse effects of environmental pollutants on human fecundity. The Carlsen report was followed by several re-analyses of their data set and by many studies on time trends in sperm quality and on secular trends in fecundity. However, the results of these studies were diverse, complex, difficult to interpret and, therefore, less straightforward than the Carlsen report suggested.
“The claims that population fecundity is declining and that environmental pollutants are involved, can neither be confirmed nor rejected, in our opinion. However, it is of great importance to find out because the possible influence of widespread environmental pollution, which would adversely affect human reproduction, should be a matter of great concern triggering large-scale studies into its causes and possibilities for prevention.
“The fundamental reason we still do not know whether population fecundity is declining is the lack of an appropriate surveillance system. Is such a system possible? In our opinion, determining total sperm counts (as a measure of male reproductive health) in combination with time to pregnancy (as a measure of couple fecundity) in carefully selected populations is a feasible option for such a monitoring system. If we want to find out whether or not population fecundity will be declining within the following 20–30 years, we must start monitoring now.”
(8) “International web survey shows high prevalence of symptomatic testosterone deficiency in men” by Tom R. Trinick et al, in Aging Male, March 2014 — Abstract…
“Though the clinical significance of testosterone deficiency is becoming increasingly apparent, its prevalence in the general population remains unrecognised. A large web-based survey was undertaken over 3 years to study the scale of this missed diagnosis.
“An online questionnaire giving the symptoms characterising testosterone deficiency syndrome (Aging Male Symptoms-AMS-scale) was set up on three web sites, together with questions about possible contributory factors.
“Of over 10,000 men, mainly from the UK and USA, who responded, 80% had moderate or severe scores likely to benefit from testosterone replacement therapy (TRT). The average age was 52, but with many in their 40s when the diagnosis of ‘late onset hypogonadism’ is not generally considered. Other possible contributory factors to the high testosterone deficiency scores reported were obesity (29%), alcohol (17.3%), testicular problems such as mumps orchitis (11.4%), prostate problems (5.6%), urinary infection (5.2%) and diabetes 5.7%.
“In this self-selected large international sample of men, there was a very high prevalence of scores which if clinically relevant would warrant a therapeutic trial of testosterone treatment. This study suggests that there are large numbers of men in the community whose testosterone deficiency is neither being diagnosed nor treated.“
For More Information
Also see this post about the effect of Xenoestrogens. hormone-disrupting or so-called ‘gender-bending’ chemicals in the environment, and the implications for human health. Also see Martin van Creveld’s provocative book Pussycats: Why the Rest Keeps Beating the West
If you liked this post, like us on Facebook and follow us on Twitter. See all posts about women and gender roles, especially these…
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- “Castle” shows a future of strong women & weak men. As for marriage…
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- Why men are avoiding work and marriage.
- Will today’s young men marry? America’s future depends which of these answers is right.
A last comparison of past and present, illustrating our collapse in testosterone levels.
