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Testosterone Replacement, Low T, HCG, & Beyond
Blood Test Discussion
Relationship Between Higher PSA and Higher SHBG
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<blockquote data-quote="Cataceous" data-source="post: 227223" data-attributes="member: 38109"><p>The formulas are not producing false results. The confusion arises because they are given in the form</p><p></p><p>FT = f(TT, SHBG, ALB)</p><p></p><p>This makes sense when you want to estimate free testosterone and the three function parameters are relatively easy to measure. However, this form creates the perception that total testosterone drives free testosterone, and also encourages the misperception that total testosterone can be treated as constant and directly under our control in the case of TRT. Instead, consider rearranging the formula to</p><p></p><p>TT = f1(FT, SHBG, ALB)</p><p></p><p>I've been arguing that this form is more natural with respect to physiology. Free testosterone is driven proportionally by the production rate of testosterone, or by the testosterone dose rate in those on TRT. The relative constancy of free testosterone allows for your observation above that "[Free testosterone] controls TTotal, so that TTotal increases or decreases porporcionalmente at the level of SHBG." If you invert the Vermeulen calculation and ignore albumin then the equation looks something like this:</p><p></p><p>TT = (a + b * FT + SHBG) * FT / (c * FT + d)</p><p></p><p>This does imply that total testosterone increases monotonically with SHBG when free testosterone is fixed.</p></blockquote><p></p>
[QUOTE="Cataceous, post: 227223, member: 38109"] The formulas are not producing false results. The confusion arises because they are given in the form FT = f(TT, SHBG, ALB) This makes sense when you want to estimate free testosterone and the three function parameters are relatively easy to measure. However, this form creates the perception that total testosterone drives free testosterone, and also encourages the misperception that total testosterone can be treated as constant and directly under our control in the case of TRT. Instead, consider rearranging the formula to TT = f1(FT, SHBG, ALB) I've been arguing that this form is more natural with respect to physiology. Free testosterone is driven proportionally by the production rate of testosterone, or by the testosterone dose rate in those on TRT. The relative constancy of free testosterone allows for your observation above that "[Free testosterone] controls TTotal, so that TTotal increases or decreases porporcionalmente at the level of SHBG." If you invert the Vermeulen calculation and ignore albumin then the equation looks something like this: TT = (a + b * FT + SHBG) * FT / (c * FT + d) This does imply that total testosterone increases monotonically with SHBG when free testosterone is fixed. [/QUOTE]
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Testosterone Replacement, Low T, HCG, & Beyond
Blood Test Discussion
Relationship Between Higher PSA and Higher SHBG
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