Purpose: Testosterone is steadily declining in an age-independent manner in Western men. A growing subset of TRP and the scientific community is becoming increasing concerned by this downward trend's consistency. In this essay we're going to take a look at the evidence for this trend's existence, explore where it surfaced, and talk about some possible solutions. Luckily, none of the solutions will involve eating a mysteriously named African root that's going to make your dick stop working.
This is the first in a series of posts which aim to facilitate community discussion of Mens' issues from a scientific perspective. You will be presented the relevant evidence, followed by my own speculation and thoughts. Regrettably, some articles can only be accessed with University credentials (paywall), so I'll quote the relevant information in addition to citing the source. I encourage everyone who can to play along at home.
Shit, This is Actually Happening...
So you've likely heard that sperm counts and testosterone have taken a nose dive (sometimes cited as up to 50%!) in the last 2 decades in Western men. Is this just an excuse by your 35 year-old single mother landlord to justify why "there's no good men left"? Unfortunately not. The claim arises from a landmark study, "A Population-Level Decline in Serum Testosterone Levels in American Men" by Travison et al . Although research on this subject is sparse, this study is rock solid as I will explain briefly.
First, however, let's review testosterone in the biological context!
Endocrine Glands and Really Big Hands (I assure you there's no problem.)
The cells of the body exist over a large spatial area and, much like the workers of Tampon-Corp (for which I am a shill), have to find a way to communicate. If the CEO lives in the brain, or more accurately the hypothalamus and pituitary gland in this case, then he has to evolve multiple methods of information dispersal covering varying distances. If he wants to tell the cell next to him "You're fired!", it's simple, all he has to do is bleb some signaling molecules in that direction that binds the "fuck off" receptor. This type of cell communication is called paracrine and only affects local cells.
However, lets say the boss wants to tell the dick cell (technical term) to proliferate or grow so the brain can swing around a 3rd leg. In that case his message needs to travel a long way, ideally using a fast moving liquid highway like the blood stream. To accomplish this the master regulator of the brain, the hypothalamus, will send the pituitary gland cell some Gonadotropin-Releasing Hormone (GnRH), and the pituitary will then release two molecules known as Leutinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH) into the blood stream. These bad boys will circulate throughout the body, eventually reaching the Leydig cells of the gonads causing the production and export of testosterone into your body. This phenomenon is known as a signaling cascade, and to be specific you've just learned about the Hypothalamic-Pituitary-Gonadal Axis (HPG Axis). Nice job, you now know more about the body than 90% of pre-med students.
Now hormones are exclusively signaling molecules and there's many complicated interactions wherein hormones trigger other glands to release a secondary hormone like above. Two of these derivative molecules are, of course, the sex hormones Testosterone and Estradial. Let's forget about estradiol for now because it makes you grow big, milky jugs.
Testosterone is a cholesterol-derived steroid hormone, meaning it has a very specific structure that allows it to pass through cell membranes, and this allows it to act on nearly every cell in the body, ultimately manifesting itself as the traits associated with sexual dimorphism. Side note: men and women respond to the molecule differently because they have different distributions of androgen receptors on their cells.
Now, Testosterone doesn't just float around in your body interacting with everything like Chad at the club. After it's synthesis in the Leydig cells of the balls, testosterone hops a ride on the protein components of the blood. A bit less than 1/3 becomes bound to serum albumin, while the other 2/3 hooks up with creatively named sex hormone-binding globulin (SHBG), with about 2% of testosterone remaining unbound and free in the blood - known as free testosterone, which has the ability to enter into cells and act .
Now that we know how testosterone exists in the blood we'll be able to better understand how it's measured. Keep this in mind because different papers use different metrics like:
- Bioavaliable Test - same as free test, 2% of total
- Total Test - free test + test bound to serum albumin and SHBG
The Landmark Study
Travison, et al. conducted a longitudinal study on 1532 men living in Boston (so we already know their test will be lower than typical ayyy). A longitudinal study is when the same group of men (referred to as a cohort), provides multiple data points over some time course t. In this case, each patient had their serum (total) testosterone and free testosterone measured at 3 periods over the course of about 25 years from 1987-2003.
Now naturally, as you know, testosterone declines as age increases. However, by cleverly utilizing a longitudinal approach to this study the researchers were able to compare different subjects' T levels at the same chronological age. In addition, Travison, et al. trimmed the sample data to reduce individuals with absurdly low or high test (under 100ng/dl or more than 1200ng/dl, respectively), and utilized self-reported metrics of health to further weed out men who developed prostate cancers or other abnormalities that may contribute to changes in T levels.
Metrics used are as follows:
- Chronic illnesses including Cancer, Heart disease, Diabetes, etc.
- Prescription meds (by number - an unfortunant weakness of this study)
- Education, Marital Status, and Socioeconomic Status
- Weight, BMI, and hip-to-waist ratio
- Cigarette smoking
- Dietary intake (in cals & as grams fat/day)
- Sedentary Activity (metric not specified here)
After deconvoluting that wealth of data and working some statistical black magic, the researchers end up reporting the following metrics.
Each year past 55 due to aging T levels were reduced by 1.6%. When adjusted for all of the above self-report metrics the rate was a decrease of 1.1% / year.
Each year for the past 20 years, the T levels of men decreased 1.2% in an age-independent manner, adjusted for above metrics resulted in a reduction of 1.0% / year.
What this means is that testosterone in the men of this cohort was decreasing as fast (roughly speaking) from an unknown source as from regular aging. This is scary stuff my dudes. Now remember how we listed off those metrics? Well we did that because the age-independent T decrease is likely coming from a source other than those listed.
As an interesting aside, in my estimation it seems pretty clear that peoples conformation to those self-reported metrics accounted for a decrease of about 0.5% annually. Might be worth thinking about.
So now that we have taken a look at the data, it's time to speculate what could actually be causing this population-level T decrease. In my last thread many people voiced their concerns and theories about this, ranging from big brother "turning the frickin' frogs gay" for population control to the role that a sedentary lifestyle might play (sitting on your balls all day ain't too great for them. Look up cyclists sperm counts if you're interested).
All of the following speculation and data was found by querying Gulag Scholar with the terms: "Testosterone Decrease, Population Testosterone Trends, Sex Hormone Trends", among other similar variations, with a filter excluding any results published prior to 1990.
Metabolic Syndrome - Eat Like Shit, Feel Like Shit
One oversight of the Travison, et al. study was that they used Diabetes as a variable in their data but left out metabolic syndrome, also known as pre-diabetes. Pitteloud, et al. conducted a study in 2005 looking at insulin sensitivity (a metric of metabolic syndrome) in men aged 25-65 years old, as well as the functioning of their HPG axis, and subsequently, serum T. The researchers also looked at the effect the blood concentration of our sex-hormone binding protein fraction (SHPG) had on total T.
Pitteloud, et al. ultimately reported a SHBG and BMI-independent correlation between serum T levels and insulin sensitivity, where if you're less pre-diabetic then your T is higher. 
Furthermore, by administering a hormone that stimulated Leydig cell production of T, the study excluded some elements of the HPG axis including the roles of leutinizing hormone and GnRH. Corroberating this study is another, Kaplan, et al, that found an extremely strong correlation between BMI, metabolic syndrome, and decreased T levels - again independent of LH and GnRH . If there is interest we can address insulin sensitivity and how to increase it in another post, as it warrants its own discussion and presentation.
Miscellaneous Other Things That Affect T
Yup. Ethanol is a testicular toxin my dudes, and it's actually a double whammy. By the way, abuse is defined in this paper as a history 3+ years with elevated markers of alcoholism. According to Maneesh, M., et al (2006), "Alcohol abusers had significantly lower plasma T with low LH and FSH" (the data shows a reduction of about 25%!) and "[ethanol] causes fertility abnormalities with low sperm count and impaired sperm [movement] in men" . The authors attribute these negative effects to the destruction of Leydig cell function by super-oxide radicals (these are basically products of normal cellular function that have extra electrons and like to fuck your shit up on the molecular level).
Moral of the story here is that if you want to drink heavily for 3+ years you might as well just chop off half of one of your balls.
Well this one was unexpected. However, in a study comparing 14 men who did not go on to become fathers with 28 men who went on to have a child, a marked reduction in T was seen . Also notable here is that the dad's had lower cortisol levels, which I found quite odd, as well as higher levels of estradiol (female sex hormone). I'm not sure what to make of this but I'm hopeful that some colorful explanations and theories will surface in the comments.
TL;DR and Conclusions
So whats the truth? What's affecting T levels across the West?
In my estimation, the most likely candidate would have to be metabolic syndrome and pre-metabolic syndrome.
I know that everyone wants to jump to the conclusion that the drops found by Travison, et al. are the result of malice or intentional hormonal sabotage, and it certainly is fun to speculate about that and I even welcome that. Regardless, the conclusion that seems evident to me is that many smaller factors are chipping away at our T levels over time, and that currently the research just isn't there to identify all the factors.
As always, I hope this post facilitates discussion of this very important issue. This has been the first post in a series of several posts exploring Mens' issues from a scientific perspective.
Thanks for reading - InvoluntarySickCunt
The next topic we will cover is aluminum-containing antiperspirants and other men's products that may be potentially dangerous, unless some other interest surfaces before then.
Sources - Read 'em and Weep
Travison, TG et al. (2007). A Population-Level Decline in Serum Testosterone Levels in American Men. The Journal of Clinical Endocrinology.
Cumming DC, Wall SR (November 1985). "Non-sex hormone-binding globulin-bound testosterone as a marker for hyperandrogenism". The Journal of Clinical Endocrinology and Metabolism. 61 (5): 873–6.
Pitteloud, N., et al (2005). Increasing insulin resistance is associated with a decrease in Leydig cell testosterone secretion in men. The Journal of Clinical Endocrinology & Metabolism, 90(5), 2636-2641.
Kaplan, S. A., et al (2006). The age related decrease in testosterone is significantly exacerbated in obese men with the metabolic syndrome. What are the implications for the relatively high incidence of erectile dysfunction observed in these men?. The Journal of urology, 176(4), 1524-1528.
Maneesh, M., et al (2006). Alcohol abuse-duration dependent decrease in plasma testosterone and antioxidants in males. Indian journal of physiology and pharmacology, 50(3), 291.
Berg, S. J., & Wynne-Edwards, K. E. (2001, June). Changes in testosterone, cortisol, and estradiol levels in men becoming fathers. In Mayo Clinic Proceedings (Vol. 76, No. 6, pp. 582-592). Elsevier.