FunkOdyssey
Seeker of Wisdom
I remember a long time ago asking the question of whether depositing a testosterone oil depot in fatty tissue surrounded by aromatase could potentially increase E2 production. The universal answer: no, it couldn't possibly, because testosterone can't aromatize until the ester is cleaved off, which only occurs in the liver.
That answer is incorrect.
www.ncbi.nlm.nih.gov
Many current T replacement therapies formulated as injections and oral preparations are T esters. Ex vivo conversion of these prodrugs to T by non-specific blood esterases after blood collection may result in overestimation of circulating T levels. Thus, in patients administered T esters, the measured T level may not only reflect circulating T but also the ex vivo conversion of the prodrug to the active androgen. This may confound hormone level evaluations as has previously been shown in the measurement of T enanthate (Wang et al., 2008) and T undecanoate (TU) (Lachance et al., 2015). Inaccurate estimation of circulating T levels may lead physicians to make improper dose adjustments in hypogonadal men treated with a T ester such as T enanthate, cypionate, and undecanoate because T levels in blood that are typically collected in plain tubes may yield falsely high T levels due to ex vivo conversion of T esters to T.
Non-specific esterases in liver, tissue, and blood cellular components hydrolyze inactive steroid esters (e.g., androgen prodrugs) into a biologically active form. The use of ester prodrugs for oral administration of androgens allows greater systemic bioavailability and a longer half-life than the active moiety (Behre, 2004). However, when blood samples are collected, the prodrug in the sample can continue to undergo hydrolysis, ex vivo, by non-specific esterases present in the blood (mainly in red and white blood cells) thus leading to overestimation of circulating androgen levels (Williams, 1985).
Now that we've established that blood contains the esterases needed to remove the ester, perhaps the reports that some people have higher E2 on SC injections should not be disregarded as biologically implausible. Maybe it's a real thing for some people, for a real reason. Something like: T ester slowly drips out of the oil depot, the ester is removed, and the first thing it encounters is a sea of aromatase.
That answer is incorrect.
Importance of measuring testosterone in enzyme-inhibited plasma for oral testosterone undecanoate androgen replacement therapy clinical trials
Testosterone undecanoate (TU) is metabolized by nonspecific esterases in blood to testosterone (T). Typical clinical practice has been to analyze testosterone in human serum. The degradation of TU to testosterone was evaluated in conditions typically ...
www.ncbi.nlm.nih.gov
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onlinelibrary.wiley.com
Many current T replacement therapies formulated as injections and oral preparations are T esters. Ex vivo conversion of these prodrugs to T by non-specific blood esterases after blood collection may result in overestimation of circulating T levels. Thus, in patients administered T esters, the measured T level may not only reflect circulating T but also the ex vivo conversion of the prodrug to the active androgen. This may confound hormone level evaluations as has previously been shown in the measurement of T enanthate (Wang et al., 2008) and T undecanoate (TU) (Lachance et al., 2015). Inaccurate estimation of circulating T levels may lead physicians to make improper dose adjustments in hypogonadal men treated with a T ester such as T enanthate, cypionate, and undecanoate because T levels in blood that are typically collected in plain tubes may yield falsely high T levels due to ex vivo conversion of T esters to T.
Non-specific esterases in liver, tissue, and blood cellular components hydrolyze inactive steroid esters (e.g., androgen prodrugs) into a biologically active form. The use of ester prodrugs for oral administration of androgens allows greater systemic bioavailability and a longer half-life than the active moiety (Behre, 2004). However, when blood samples are collected, the prodrug in the sample can continue to undergo hydrolysis, ex vivo, by non-specific esterases present in the blood (mainly in red and white blood cells) thus leading to overestimation of circulating androgen levels (Williams, 1985).
Now that we've established that blood contains the esterases needed to remove the ester, perhaps the reports that some people have higher E2 on SC injections should not be disregarded as biologically implausible. Maybe it's a real thing for some people, for a real reason. Something like: T ester slowly drips out of the oil depot, the ester is removed, and the first thing it encounters is a sea of aromatase.
