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Testosterone: Difference between revisions
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→Secular decline in T-levels of Western men
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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 reason why SHBG is lowering is likely 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. | 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 reason why SHBG is lowering is likely 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. | ||
Serum 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. | Serum 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. | ||
This is crucial, as | 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. | ||
Cross-national and cross-temporal difference in diet and general lifestyle also likely play much of a role in determining the hormonal profile of men from said countries and periods. For example, intakes of dietary protein in wealthy Western countries are generally higher than in developing countries,<ref>https://www.wri.org/data/people-are-eating-more-protein-they-need-especially-wealthy-regions</ref> which together with dietary fibre intake also being negatively correlated with country level economic development,<ref>https://www.robertbarrington.net/fibre-intake-various-countries/</ref> would result in lower levels of SHBG in the bloodstream, which would again lead to the bodies of Western individuals being generally more sensitive to the effects of T compared to people in developing countries.<ref>https://academic.oup.com/jcem/article/85/1/293/2854619?login=true</ref> | Cross-national and cross-temporal difference in diet and general lifestyle also likely play much of a role in determining the hormonal profile of men from said countries and periods. For example, intakes of dietary protein in wealthy Western countries are generally higher than in developing countries,<ref>https://www.wri.org/data/people-are-eating-more-protein-they-need-especially-wealthy-regions</ref> which together with dietary fibre intake also being negatively correlated with country level economic development,<ref>https://www.robertbarrington.net/fibre-intake-various-countries/</ref> would result in lower levels of SHBG in the bloodstream, which would again lead to the bodies of Western individuals being generally more sensitive to the effects of T compared to people in developing countries.<ref>https://academic.oup.com/jcem/article/85/1/293/2854619?login=true</ref> | ||