US testosterone levels dropping?

[RivkahChaya]

Some OTC “supplement” is advertising on TV that it makes men men, by upping their testosterone, and it will give you THE FIRST BOTTLE FREE!!!

The ad starts out by stating unequivocally that “men today” (whatever that means) have lower testosterone levels than their fathers did, who in turn have lower testosterone levels than their fathers. OMG! The country is having a masculinity crisis! You actually have a patriotic duty to buy this product.

Now, I’m sure the product is BS, but I’m wondering about the claim that the country’s testosterone level is dropping.

Is this part even true? If it is, what is the reason?

I can think of some benign reasons for it, such as the fact that men’s testosterone levels drop with age, and the population is aging, thanks to Baby Boomers now being grandparents, so yes, on the whole, the country’s testosterone level could be lower than it was when the Boomers were in their early 20s.

But I wondered about a few other things. One thing I wondered about is medications for hair loss. Hair loss is caused by testosterone, no it would make sense that cremes that cause hair to grow thicker block testosterone reception, and after you use them long enough, your testosterone level might just drop.

I also thought about the fact that many men who survive cancer become sterile. I don’t know what the exact mechanism for this is, but I can imagine some that involve a drop in testosterone, so advances in cancer therapy could be a cause as well.

After all, the ad does not state (albeit it, it implies) that every individual man in the US has less testosterone than his literal father, as opposed to looking at averages. I think it’s pretty clear the data, if it exists, involves averages.

So, has anyone heard anything? Know anything specific? Anything about cause, if it is true?

PS to mods: I started out in GQ, but I realize that depending on the type of answers, this may get moved.

[engineer_comp_geek]

I poked around a bit on google. I found numerous news stories, most of which seemed to be based on two actual studies, one in the U.S. and one in Denmark. Both studies found a decline in testosterone levels, so that claim does seem to be true.

Study of U.S. men:

A Population-Level Decline in Serum Testosterone Levels in American Men

Study of Danish men:

Secular decline in male testosterone and sex hormone binding globulin serum...

Both studies were published in 2007.

Neither study came to a conclusion about the causes behind this, however. Also, the studies saw a drop in testosterone levels of men of the same age, meaning that this cannot be attributed to an aging population.

Many of the articles that I found discussed theories about why this might be, but none cited any studies to support their claims. It seems that there is a lot of speculation on the subject, but little proof of any particular theory.

@RivkahChaya

After all, the ad does not state (albeit it, it implies) that every individual man in the US has less testosterone than his literal father, as opposed to looking at averages. I think it’s pretty clear the data, if it exists, involves averages.

The data does exist, and you are correct, it involves averages.

[bob_2]

It’s not just testosterone - sperm counts are taking a dive too.

A rigorous and comprehensive meta-analysis of data collected between 1973 and 2011 finds that among men from Western countries, sperm concentration declined by more than 50 percent, with no evidence of a ‘leveling off’ in recent years
Significant ongoing decline in sperm counts of Western men | ScienceDaily

[Ulfreida]

Maybe humans are solving their overpopulation problem just fine! Silly me, to worry.

[DinoR]

There may be some lifestyle component as well. We’re more likely to be overweight now. For those who start overweight with low testosterone, losing weight is correlated with increased testosterone levels.

[DSeid]

There are many factors that impact or at least correlate with testosterone levels in males. Which ones are at play here?

Men in committed, romantic relationships have lower testosterone.

Results revealed that men in committed, romantic relationships had 21% lower testosterone levels than men not involved in such relationships.

Longitudinal evidence that fatherhood decreases testosterone in human males.

In species in which males care for young, testosterone (T) is often high during mating periods but then declines to allow for caregiving of resulting offspring … Consistent with the hypothesis that child interaction suppresses T, fathers reporting 3 h or more of daily childcare had lower T at follow-up compared with fathers not involved in care (P < 0.05). Using longitudinal data, these findings show that T and reproductive strategy have bidirectional relationships in human males, with high T predicting subsequent mating success but then declining rapidly after men become fathers. Our findings suggest that T mediates tradeoffs between mating and parenting in humans, as seen in other species in which fathers care for young.

As mentioned, obesity results in lower testosterone and lower sperm counts.

Environmental endocrine disruptors, such as phthalates, may have long term impacts on testicular function.
So several hypotheses can be generated easily, from a change in the role of men in society (e.g. more involved fatherhood, less frequency of direct male-male competition), to obesity rates, to environmental disruptors with possible even prenatal impacts, and more. Hard to know which ones are operative.

[DSeid]

Another possible input.

Women using the birth control pill prefer men with less masculine faces compared to nonusers, new research suggests.

Millions of women use hormonal forms of contraception, and some studies indicate the pill could affect partner preferences. A new study shows women were attracted to less masculine male faces after going on the pill, while their ratings of the attractiveness of female faces were unaffected. And in couples who first met when the woman was on the pill, the men were less likely to have manly faces than those who met when the woman was off the pill.

The Pill became more ubiquitous in the late 60s. So we are about a half century into many women making mate selections while on it. IF males with less masculine faces reflect a genetic propensity to produce less testosterone, then we may be seeing selection for a next generation of males that produce less testosterone compared to previous generations.

[pool]

You also can’t discount the fact that most men in the U.S. dont get enough sleep, and are in fact chronically missing the 7-8 hours they need a night. Abuse of drugs is prob another factor, opiates, alcohol, pretty much anything that makes you have a good time lowers testosterone. Men probably spend less time outdoors, synthesizing vitamin D which is necessary for testosterone production. All the processed crap, and pthalates as Dseid mentioned.

I read an interesting thing the other day about how the Y chromosome appears to be shrinking every generation, sounds scary.

[RivkahChaya]

Wow. Interesting. Thanks to all who responded.

[HoneyBadgerDC]

I will give the retired truck mechanics opinion on this. In the animal world there is a direct correlation between competing and generating testosterone. When you feel either beaten or non competitive I suspect a mans levels will drop. Men and boys have rituals we go through that simulate fighting and aggression where no one looses. It is a very safe way to generate testosterone. We rely on other men to help boost our levels. When the rituals are no longer practiced less of us have access to testosterone generating behavior. Men in power and wealthy men seem to also have high levels of testosterone, they are winners and feel dominant. At 70 years old I have experienced what I think is a drop in my levels. I spent my entire life as a shop foreman or boss. Once retired I am just me. I actually am enjoying a less competitive world with slightly less sex drive.