Testosterone: Difference between revisions

[[file:578px-Testosteron.svg.png|thumb|right|350x|The chemical structure of testosterone.]]

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).

The influence of androgens in driving these changes does not seem limited to the prenatal environment or puberty (periods when the organism is particularly sensitive to the masculinizing effects of T). However, most of the physiological, cognitive, and behavioral effects resulting from the administration of exogenous sex hormones to adults seem small apart from the specific cases regarding the administration of opposite sex hormones to transgenders,<ref>https://pubmed.ncbi.nlm.nih.gov/27347894/</ref> with the notable exception of the dramatic effects anabolic steroid use can have on the promotion of lean tissue growth.<ref>https://www.strongerbyscience.com/much-steroids-increase-hypertrophy/</ref><ref>https://www.strongerbyscience.com/steroids-and-strength-differences/</ref>

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==

This is crucial, as some men have high serum T levels because their level of SHBG is high, which means most of the T they produce is effectively useless. Generally the body tries to maintain strong homeostasis when it comes to hormones.  

These are all factors that need to be taken into account when trying to examine cohort level differences in hormonal profiles.

This is important 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==

In many animals, testosterone has a positive relationship to [[dominance hierarchy|male dominance status]].<ref>https://onlinelibrary.wiley.com/doi/abs/10.1002/ajpa.20387</ref><ref>https://www.sciencedirect.com/science/article/abs/pii/S0018506X0800161X</ref>

Higher T levels may be more strongly related to the attainment of dominance in social milieus based around violent domination as opposed to ones based around social consensus, competence, and likability.<ref>https://www.tandfonline.com/doi/abs/10.1080/19485565.2006.9989114</ref> This is similar to the conclusions of research into [[FWHR|male facial-width-to-height ratio]], another trait linked to status drive and dominance, which has discovered that this characteristic is only linked to violence in men of lower socio-economic status.<ref>https://pubmed.ncbi.nlm.nih.gov/30412629/</ref>

Not surprisingly, a man's level of muscularity is a major factor in other men's determinations of that man's level of social dominance, social threat and capacity for violence. Muscularity also seems to be strongly linked to mating success in certain social contexts, such as among university students in fraternities, an effect that appears mediated by other men's perceptions of muscular men's physical dominance.<ref>https://incels.wiki/w/Scientific_Blackpill#Among_male_university_students.2C_only_cues_of_physical_dominance_over_other_men_predicted_their_mating_success</ref>

Some research has indicated that children that have received higher levels of exposure to prenatal androgens had lower quality social relationships and more restricted interests (boys only in this sample) essentially implicating higher neurological masculization in the development of (sub-clinical) autistic traits,<ref>https://pubmed.ncbi.nlm.nih.gov/15679528/</ref> in line with the extreme male brain theory of autism. As even subclinical autistic traits seem to be linked to less social connectedness and loneliness<ref>https://link.springer.com/article/10.1007/s10803-018-3812-6</ref> it therefore likely that exposure to excess levels of testosterone in the prenatal environment is associated with lower social status, less romantic success and other negative social outcomes, suggesting that this trait is subject to significant balancing selection in modern society.  

Together with the general [[feminization]] of post-industrial Western society, this may result in [[evolutionary mismatch|evolutionary mismatches]] wherein excess levels of masculinity and (certain) testosterone-related traits may be generally associated with lower social status. Other research has indicated that the broader autism phenotype (BAP) may have had certain adaptive qualities that were evolutionarily selected for in the past, suggesting that neurological masculinzation may previously benefited males [[reproductive success]].<ref>https://www.proquest.com/openview/3b780f7e3a7306b98c528f5dcea7bc46/1?pq-origsite=gscholar&cbl=18750</ref>

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>

It is very likely that testosterone does not mediate any of these status-seeking behaviors on its own to a substantial degree, as interactions with other hormones such as cortisol,<ref>https://www.sciencedirect.com/science/article/abs/pii/S030645301500400X</ref> estrogen, prolactin, and various neurotransmitters such as serotonin<ref>https://link.springer.com/article/10.1007/s11031-011-9264-3</ref> appear crucial in driving many of the behaviors linked to "high-T" in the popular imagination.

==T and sexual behavior==

Testosterone does seem to generally drive greater reproductive effort in males, and it is a highly replicable finding that men in committed relationships tend to have lower testosterone levels (though the effect is generally weak<ref>https://www.sciencedirect.com/science/article/pii/S0306453019301271</ref>), possibly to promote greater pair-bonding in males.<ref>https://www.sciencedirect.com/science/article/abs/pii/S0018506X19300030</ref> Part of this link between lower T and being in a committed relationship may not be casual. Instead, it may stem from the apparent fact that lower testosterone men may be more pro-social, more generous to their female partners and that men with higher testosterone seem to have larger levels of conflict in their relationships, particularly in egalitarian societies that seek to reduce status competition among males.<ref>https://www.nature.com/articles/s41598-020-70958-3</ref> Thus men in committed relationships may be partly selected for low-T.

A link between testosterone (and physical masculinization) and non-committal sexual strategies indicates that T is generally linked to a [[life history|fast life history]] strategy based around maximizing mating effort and minimizing parental care, a strategy that many high-T men seem unable to operationalize effectively in light of these weak effects for sexual success and T.

==Dual hormone hypothesis==

The dual hormone hypothesis states that testosterone substantially interacts with the stress hormone cortisol in order to exert its assumed affects on dominance behavior and mating drive. Cortisol is thought to inhibit these effects when levels are high, and androgens generally have the effect of inhibiting cortisol release. Thus the ratio between the two hormones is thought to be more important than levels of either one on their own, in terms of driving behaviors such as approach/avoidance, status seeking, violence, and sex drive.

For example, some evidence shows increased testosterone shows no relation to increased male sexual desire with the concurrent presence of high cortisol levels.

The fact that increased testosterone alone doesn't increase male sex drive provides some support for the dual hormone hypothesis. It is said some effects of testosterone become potentiated in the presence of lower levels of the stress hormone cortisol and suppressed when higher levels of this hormone are present.<ref>https://psyarxiv.com/42t6e/</ref>

==See also==

* [[Anabolic steroid]]

* [[Dominance hierarchy]]

==References==

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