6,353
edits
Testosterone: Difference between revisions
Jump to navigation
Jump to search
m
no edit summary
mNo edit summary |
mNo edit summary |
||
| Line 1: | Line 1: | ||
'''Testosterone''' is a [[anabolic steroid|steroid]] and the primary male sex hormone (androgen). Its effects on the body result from the direct activation of the androgen receptors found in various tissues across the body or via its metabolism to other androgens, most notably via the actions of the enzyme 5-α-reductase, which converts testosterone to the far more potent androgen dihydrotestosterone (DHT). | '''Testosterone''' is a [[anabolic steroid|steroid]] and the primary male sex hormone (androgen). Its effects on the body result from the direct activation of the androgen receptors found in various tissues across the body or via its metabolism to other androgens, most notably via the actions of the enzyme 5-α-reductase, which converts testosterone to the far more potent androgen dihydrotestosterone (DHT). | ||
In humans, testosterone and other androgens are crucial for the development and maintenance of several male sexually dimorphic traits, such as men's greater bone density and muscle mass compared to women, and (mainly via the process of conversion to DHT | In humans, testosterone and other androgens are crucial for the development and maintenance of several male sexually dimorphic traits, such as men's greater bone density and muscle mass compared to women, and (mainly via the process of conversion to DHT, which exhibits far stronger affinity for the AR in these tissues) the development of fixed masculine traits during puberty, such as androgenic body hair, enlargement of the male sex organs, and greater vocal depth. Despite the common perception of it as a male hormone, it is also produced by women in much smaller amounts (in ovaries and the adrenal glands), and it seems to play an essential role in the maintenance of several vital physiological functions in women, particularly the [[sex drive|libido]].<ref>https://www.sciencedirect.com/science/article/abs/pii/S2213858715002843</ref> | ||
Testosterone and estrogen are nearly identical in terms of their chemical structure, and in men, estrogen is produced via the conversion of T to estrogen via the process of {{W|aromatization|aromatization}}. Estrogen is important to men's general health due to estrogen's enhancing effects on libido, bone health and its neuroprotective nature. In men that are particularly sensitive to estrogen, aromatization may result in feminizing effects such as the development of breast tissue (gynecomastia). | Testosterone and estrogen are nearly identical in terms of their chemical structure, and in men, estrogen is produced via the conversion of T to estrogen via the process of {{W|aromatization|aromatization}}. Estrogen is important to men's general health due to estrogen's enhancing effects on libido, bone health and its neuroprotective nature. In men that are particularly sensitive to estrogen, aromatization may result in feminizing effects such as the development of breast tissue (gynecomastia). | ||
| Line 8: | Line 8: | ||
In humans (and other animals), testosterone plays a role in driving increased aggression, violent behavior, and status drive.<ref>https://web.archive.org/web/20160109111144/http://www.homepage.psy.utexas.edu/HomePage/faculty/josephs/pdf_documents/Arch_Chall_NBR.pdf</ref> | In humans (and other animals), testosterone plays a role in driving increased aggression, violent behavior, and status drive.<ref>https://web.archive.org/web/20160109111144/http://www.homepage.psy.utexas.edu/HomePage/faculty/josephs/pdf_documents/Arch_Chall_NBR.pdf</ref> | ||
There has been a secular decline in testosterone 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 testosterone 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. | 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. | ||
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. | |||
==T and social dominance== | ==T and social dominance== | ||
| Line 27: | Line 27: | ||
Some traits that are linked to higher levels of testosterone exposure in the womb, such as systematizing, may also promote the attainment of social status and wealth, leading to higher fitness and reproductive success. It is plausible that a shift from mating systems based around [[arranged marriage]] and female economic dependence on men towards greater female mate choice together with a greater tendency towards hierarchies being based around likability sheer competence in modern service economies has resulted in lowered sexual success for men that are prone towards systematizing, thus leading to yet another potential evolutionary mismatch. | Some traits that are linked to higher levels of testosterone exposure in the womb, such as systematizing, may also promote the attainment of social status and wealth, leading to higher fitness and reproductive success. It is plausible that a shift from mating systems based around [[arranged marriage]] and female economic dependence on men towards greater female mate choice together with a greater tendency towards hierarchies being based around likability sheer competence in modern service economies has resulted in lowered sexual success for men that are prone towards systematizing, thus leading to yet another potential evolutionary mismatch. | ||
Another potential factor that serves to mask effects in research that examines the link between status and testosterone is that these studies often do not take into account the effects that the release of short bursts of T may play in mediating to outcome of dominance contests. However, a growing literature on the "challenge hypothesis" of testosterone does. The challenge hypothesis states that testosterone will rise in men in contexts where male intersexual competition is particularly salient, such as male dominance | Another potential factor that serves to mask effects in research that examines the link between status and testosterone is that these studies often do not take into account the effects that the release of short bursts of T may play in mediating to outcome of dominance contests. However, a growing literature on the "challenge hypothesis" of testosterone does. The challenge hypothesis states that testosterone will rise in men in contexts where male intersexual competition is particularly salient, such as during or after male dominance contests or in the presence of fertile females.<ref>https://www.sciencedirect.com/science/article/abs/pii/S0018506X08002183</ref> | ||
Evidence for this hypothesis in human samples is mixed, but does generally support the thesis that male testosterone levels are reactive in response to male intrasexual competition related cues, particularly in response to victory in status competitions.<ref>https://www.sciencedirect.com/science/article/abs/pii/S0018506X16300198</ref> | Evidence for this hypothesis in human samples is mixed, but does generally support the thesis that male testosterone levels are reactive in response to male intrasexual competition related cues, particularly in response to victory in status competitions.<ref>https://www.sciencedirect.com/science/article/abs/pii/S0018506X16300198</ref> | ||