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Testosterone: Difference between revisions
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One should take studies on the effects of testosterone on driving certain psychological changes should be taken with a grain of salt, as many studies that examine the effects of testosterone (and other hormones) on psychology are deeply flawed. A large amount of these kinds of studies do not take these inter-hormone interactions into account, do not use particularly reliable measures of testosterone, have low sample sizes, do not take into account interindividual differences in sensitivity to androgens, and do not take into account the effects prenatal and pubertal 'priming' may have on shaping the body's response to testosterone in adulthood. Adult T-levels are also substantially affected by lifestyle factors<ref>https://academic.oup.com/jcem/article/92/2/549/2566787?login=true</ref><ref>https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1019.6064&rep=rep1&type=pdf</ref> such as age, smoking, body fat percentage and general health, which is likely another confounding factor in such studies. | One should take studies on the effects of testosterone on driving certain psychological changes should be taken with a grain of salt, as many studies that examine the effects of testosterone (and other hormones) on psychology are deeply flawed. A large amount of these kinds of studies do not take these inter-hormone interactions into account, do not use particularly reliable measures of testosterone, have low sample sizes, do not take into account interindividual differences in sensitivity to androgens, and do not take into account the effects prenatal and pubertal 'priming' may have on shaping the body's response to testosterone in adulthood. Adult T-levels are also substantially affected by lifestyle factors<ref>https://academic.oup.com/jcem/article/92/2/549/2566787?login=true</ref><ref>https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1019.6064&rep=rep1&type=pdf</ref> such as age, smoking, body fat percentage and general health, which is likely another confounding factor in such studies. | ||
==Secular decline in T-levels of Western men== | ==Secular decline in T-levels of Western men== | ||
There has been a secular decline in male T levels in Western countries that is independent of factors such as population aging and increased obesity,<ref>https://academic.oup.com/jcem/article/92/1/196/2598434?login=true</ref> leading to sensationalist headlines regarding rampant [[soyboy|feminization]] of men being driven by this factor alone. However, other longitudinal studies have found concurrent evidence that sex-hormone-binding globulin (SHBG), a protein that binds to testosterone and makes it inert in the body, has also been decreasing on a population and cohort level.<ref>https://academic.oup.com/jcem/article/92/12/4696/2597312?login=true</ref> | There has been a secular decline in male T levels in Western countries that is independent of factors such as population aging and increased obesity,<ref>https://academic.oup.com/jcem/article/92/1/196/2598434?login=true</ref> leading to sensationalist headlines regarding rampant [[soyboy|feminization]] of men being driven by this factor alone. However, other longitudinal studies have found concurrent evidence that sex-hormone-binding globulin (SHBG), a protein that binds to testosterone and makes it inert in the body, has also been decreasing on a population and cohort level.<ref>https://academic.oup.com/jcem/article/92/12/4696/2597312?login=true</ref> | ||
If this finding proves robust, this reduction in SHBG would result in less negative feedback being exerted on men's hypothalamic-pituitary-gonadal axis (HPG axis), which would lead to the body downregulating T production as it essentially needs less to produce the desired effects. Meaning the secular decrease in T wouldn't be particularly relevant in driving any practical differences in population level masculinization. SHBG is likely lowering due to | If this finding proves robust, this reduction in SHBG would result in less negative feedback being exerted on men's hypothalamic-pituitary-gonadal axis (HPG axis), which would lead to the body downregulating T production as it essentially needs less to produce the desired effects. Meaning the secular decrease in T wouldn't be particularly relevant in driving any practical differences in population level masculinization. SHBG is likely lowering due to increasing obesity, meaning that obese men would often have lower T levels (due to higher aromatization of T to estrogen, as the fat cells contain the aromatase enzyme<ref>https://pubmed.ncbi.nlm.nih.gov/11399122/</ref>) but would also be more sensitive to the testosterone they do produce. | ||
Free testosterone levels are far less clinically relevant than levels of unbound (free) testosterone, so what is important to establish a real decline in T levels would be to prove that levels of free-testosterone are falling. | Free testosterone levels are far less clinically relevant than levels of unbound (free) testosterone, so what is important to establish a real decline in T levels would be to prove that levels of free-testosterone are falling. | ||
Another flaw with many of these studies is that they do not control for the fact that smoking has massively decreased in Western countries,<ref>https://ncci.canceraustralia.gov.au/prevention/smoking-prevelance/smoking-prevalence-adults</ref> with cigarette consumption peaking in the 1950s and falling to low levels in the modern era.<ref>https://ourworldindata.org/smoking</ref> | Another flaw with many of these studies is that they do not control for the fact that smoking has massively decreased in Western countries,<ref>https://ncci.canceraustralia.gov.au/prevention/smoking-prevelance/smoking-prevalence-adults</ref> with cigarette consumption peaking in the 1950s and falling to low levels in the modern era.<ref>https://ourworldindata.org/smoking</ref> | ||
This is because smoking is correlated with higher free and total serum testosterone levels,<ref>https://pubmed.ncbi.nlm.nih.gov/31528824/</ref> a link that is not known to be casual (it could be due to T being linked to impulsiveness and risk taking etc.), though it likely is to some degree as tobacco | This is because smoking is correlated with higher free and total serum testosterone levels,<ref>https://pubmed.ncbi.nlm.nih.gov/31528824/</ref> a link that is not known to be casual (it could be due to T being linked to impulsiveness and risk taking etc.), though it likely is to some degree as nicotine and other compounds found in tobacco have moderate anti-aromatase properties.<ref>https://www.researchgate.net/publication/232974519_Potential_Contribution_of_Aromatase_Inhibition_to_the_Effects_of_Nicotine_and_Related_Compounds_on_the_Brain</ref> The inhibition of the aromatase enzyme would lead to increased T levels as the body would tend to compensate for the lower estrogen levels by increasing testosterone production.<ref>https://www.getroman.com/health-guide/anastrozole-improve-testosterone/</ref> | ||
==T and social dominance== | ==T and social dominance== | ||