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Testosterone Replacement, Low T, HCG, & Beyond
Blood Test Discussion
SHBG cause or consequence of hypogonadism?
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<blockquote data-quote="Cataceous" data-source="post: 230043" data-attributes="member: 38109"><p>I'm not sure if this is the paper, but it still has lots of good stuff:</p><p>[URL unfurl="true"]https://academic.oup.com/edrv/article/38/4/302/3897170[/URL]</p><p></p><p style="margin-left: 20px"><em>If the free hormone hypothesis is correct, an increase in SHBG concentrations would transiently decrease free testosterone concentrations, which would trigger the feedback and feed-forward mechanisms within the hypothalamic-pituitary-testicular axis to stimulate luteinizing hormone (LH) and testosterone production until free testosterone levels were restored.</em></p><p>...</p><p style="margin-left: 20px"><em>Some men with HIV may have markedly elevated SHBG levels (162), leading to high-normal or high total testosterone levels, even though free testosterone levels in a significant fraction of men with HIV were low normal or even low in the face of elevated total testosterone levels (163–165), leading many HIV experts to recommend measurement of free testosterone levels in the evaluation of hypogonadism in this population (166).</em></p><p>...</p><p style="margin-left: 20px"><em>Patients with undetectable SHBG concentrations serve as unique experiments of nature for examining the free hormone hypothesis. Vos et al. (172) recently identified a brother and sister pair who were homozygous for a missense mutation within the SHBG gene (p.G224R SHBG), resulting in retention of the mutant protein in the endoplasmic reticulum, failure to secrete SHBG, and undetectable serum SHBG levels. As expected with an undetectable SHBG level, the male patient with SHBG deficiency had a very low total testosterone level of 4.8 nmol/L (reported normal range, 10 to 30 nmol/L) but a normal free testosterone level (174 pmol/L; normal range of the assay, 120 to 750 pmol/L). Both siblings had normal gonadal development and function. Furthermore, the LH level in the male was not elevated, and he had normal sexual development and normal secondary sex characteristics with normal spermatogenesis, suggesting that free testosterone concentrations, rather than total testosterone concentrations, regulate sexual development and feedback inhibition of gonadotropins.</em></p><p>...</p><p style="margin-left: 20px"><em>Transgenic male mice that hyperexpress human SHBG had markedly elevated serum total testosterone levels that were 10 to 100 times higher than those in wild-type littermates (184). Despite markedly elevated total testosterone levels, free testosterone concentrations and reproductive function in these mice were normal (185), providing further support for the free hormone hypothesis.</em></p></blockquote><p></p>
[QUOTE="Cataceous, post: 230043, member: 38109"] I'm not sure if this is the paper, but it still has lots of good stuff: [URL unfurl="true"]https://academic.oup.com/edrv/article/38/4/302/3897170[/URL] [INDENT][I]If the free hormone hypothesis is correct, an increase in SHBG concentrations would transiently decrease free testosterone concentrations, which would trigger the feedback and feed-forward mechanisms within the hypothalamic-pituitary-testicular axis to stimulate luteinizing hormone (LH) and testosterone production until free testosterone levels were restored.[/I][/INDENT] ... [INDENT][I]Some men with HIV may have markedly elevated SHBG levels (162), leading to high-normal or high total testosterone levels, even though free testosterone levels in a significant fraction of men with HIV were low normal or even low in the face of elevated total testosterone levels (163–165), leading many HIV experts to recommend measurement of free testosterone levels in the evaluation of hypogonadism in this population (166).[/I][/INDENT] ... [INDENT][I]Patients with undetectable SHBG concentrations serve as unique experiments of nature for examining the free hormone hypothesis. Vos et al. (172) recently identified a brother and sister pair who were homozygous for a missense mutation within the SHBG gene (p.G224R SHBG), resulting in retention of the mutant protein in the endoplasmic reticulum, failure to secrete SHBG, and undetectable serum SHBG levels. As expected with an undetectable SHBG level, the male patient with SHBG deficiency had a very low total testosterone level of 4.8 nmol/L (reported normal range, 10 to 30 nmol/L) but a normal free testosterone level (174 pmol/L; normal range of the assay, 120 to 750 pmol/L). Both siblings had normal gonadal development and function. Furthermore, the LH level in the male was not elevated, and he had normal sexual development and normal secondary sex characteristics with normal spermatogenesis, suggesting that free testosterone concentrations, rather than total testosterone concentrations, regulate sexual development and feedback inhibition of gonadotropins.[/I][/INDENT] ... [INDENT][I]Transgenic male mice that hyperexpress human SHBG had markedly elevated serum total testosterone levels that were 10 to 100 times higher than those in wild-type littermates (184). Despite markedly elevated total testosterone levels, free testosterone concentrations and reproductive function in these mice were normal (185), providing further support for the free hormone hypothesis.[/I][/INDENT] [/QUOTE]
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Testosterone Replacement, Low T, HCG, & Beyond
Blood Test Discussion
SHBG cause or consequence of hypogonadism?
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