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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone Basics & Questions
Low SHBG and Estradiol
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<blockquote data-quote="Cataceous" data-source="post: 159322" data-attributes="member: 38109"><p>"... SHBG has minimal if any effect on the apparent serum half-life of testosterone. However, lower SHBG does result in proportionally lower total testosterone for the same input (dose)."</p><p></p><p>The first point is pretty straightforward. After you inject a testosterone ester there's an oily deposit under the skin or in the muscle. This depot slowly dissolves, releasing the ester, which results in a steady flow of testosterone into circulation. It's this flow rate that determines the apparent half-life of testosterone. There is no obvious way for SHBG to influence this flow of testosterone into circulation.</p><p></p><p>The confusion arises because of the relationship between free T, total T and SHBG; at a fixed total T, lower SHBG means higher free T. The clearance rate of testosterone is proportional to free T, so you'd infer that lower SHBG means faster excretion. But this is turned around, because under TRT the flow of testosterone is fixed, on average. This means that the excretion rate is also fixed, which implies a constant free T, as long as other metabolic factors don't vary in this time frame—and I do not see claims that they do.</p><p></p><p>If you accept this premise then total T becomes the dependent variable, determined by SHBG and free T. From this it follows directly that lower SHBG implies lower total testosterone.</p><p></p><p>There are a couple of known problems with low SHBG. First is that it leads to relatively higher free estradiol. And second, in some locations testosterone is delivered directly by SHBG, so a dearth of SHBG might leave these cells without enough testosterone.</p></blockquote><p></p>
[QUOTE="Cataceous, post: 159322, member: 38109"] "... SHBG has minimal if any effect on the apparent serum half-life of testosterone. However, lower SHBG does result in proportionally lower total testosterone for the same input (dose)." The first point is pretty straightforward. After you inject a testosterone ester there's an oily deposit under the skin or in the muscle. This depot slowly dissolves, releasing the ester, which results in a steady flow of testosterone into circulation. It's this flow rate that determines the apparent half-life of testosterone. There is no obvious way for SHBG to influence this flow of testosterone into circulation. The confusion arises because of the relationship between free T, total T and SHBG; at a fixed total T, lower SHBG means higher free T. The clearance rate of testosterone is proportional to free T, so you'd infer that lower SHBG means faster excretion. But this is turned around, because under TRT the flow of testosterone is fixed, on average. This means that the excretion rate is also fixed, which implies a constant free T, as long as other metabolic factors don't vary in this time frame—and I do not see claims that they do. If you accept this premise then total T becomes the dependent variable, determined by SHBG and free T. From this it follows directly that lower SHBG implies lower total testosterone. There are a couple of known problems with low SHBG. First is that it leads to relatively higher free estradiol. And second, in some locations testosterone is delivered directly by SHBG, so a dearth of SHBG might leave these cells without enough testosterone. [/QUOTE]
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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone Basics & Questions
Low SHBG and Estradiol
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