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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone and Men's Health Articles
Male infertility and intratesticular T - insight into novel serum biomarkers
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<blockquote data-quote="madman" data-source="post: 217415" data-attributes="member: 13851"><p><em><strong>*Intratesticular testosterone is vital for spermatogenesis, male fertility, and virility</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*<em>Testosterone is the principal hormone responsible for both spermatogenesis and fertility, as well as the development of primary male sexual characteristics</em></strong></em></p><p><em><strong></strong></em></p><p><em><strong>*Testis, therefore, has the dual function of virility via testosterone and fertility via spermatozoa respectively, the two being naturally intertwined </strong></em></p><p><em><strong></strong></em></p><p><em><strong>*Once cholesterol is converted into testosterone by Leydig cells, it then acts to promote spermatogenesis by acting on androgen receptors (ARs) found on Leydig, Sertoli, and peritubular cells. <u>Still, GnRH is the precursor of both virility and fertility, and gonadotropin withdrawal naturally leads to the failure of spermatogenesis</u>. <u>This last statement is mainly due to the loss of testosterone production, as FSH is dispensable for male fertility, but LH is needed</u> </strong></em></p><p><em><strong></strong></em></p><p><em><strong>*Testosterone, and more specifically, intratesticular testosterone (ITT) levels are essential to male fertility </strong></em></p><p><em><strong></strong></em></p><p><em><strong>*ITT and FSH are required to remain at consistently high levels to maintain normal spermatogenesis</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*A normal male’s ITT levels range between 400-600 ng/g while their serum levels are usually almost 100x lower</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*All in all, the Leydig cell acts as a vital mediator between the HPG axis and the effect of androgens on fertility, hence leading to the intratesticular environment necessary to conserve both fertility and virility</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*Although significant, <u>FSH alone cannot complete the necessary cycle of spermatogenesis</u>.</strong> <strong>Similarly, even though an absence of FSH may lead to spermatogenic impairment, <u>decreased levels of ITT would completely abolish spermatogenesis</u>.</strong></em></p><p><em><strong></strong></em></p><p><em><strong>17-OHP is an intermediate steroid synthesized within the adrenal gland zona fasciculata and the testes. 70% of the circulating 17-OHP is derived from the testes and the rest is thought to originate from the adrenal gland</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*Similar to testosterone, 17-OHP is also regulated by the HPG axis and undergoes diurnal variation mirroring testosterone, with peaks in the morning and falls by the evening to 60% of its original high point</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*INSL3 is a peptide hormone synthesized in adult Leydig cells and has been previously shown to be able to act as a biomarker for Leydig cell functionality</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*Inhibin B is a dimeric glycoprotein whose bioactivity is dependent on its dimerization of its respective α and βB subunits. Its function is representative of Sertoli cells, acting as a negative regulator to pituitary FSH</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*Standard ITT was found to be around 170 times higher than serum testosterone and did not correlate with serum LH, FSH, testosterone, DHT (dihydrotestosterone), or estradiol </strong></em></p><p><em><strong></strong></em></p><p><em><strong>*DHT was found to be only 11 times higher within the testes than in the serum, likely due to the fact that most of it is made by the conversion of 5-alpha reductase in peripheral tissue [49] (<u>most of which is concentrated to the prostate with minimal expression in genital skin</u>), as further shown in Fig. 2 </strong></em></p></blockquote><p></p>
[QUOTE="madman, post: 217415, member: 13851"] [I][B]*Intratesticular testosterone is vital for spermatogenesis, male fertility, and virility *[I]Testosterone is the principal hormone responsible for both spermatogenesis and fertility, as well as the development of primary male sexual characteristics[/I] *Testis, therefore, has the dual function of virility via testosterone and fertility via spermatozoa respectively, the two being naturally intertwined *Once cholesterol is converted into testosterone by Leydig cells, it then acts to promote spermatogenesis by acting on androgen receptors (ARs) found on Leydig, Sertoli, and peritubular cells. [U]Still, GnRH is the precursor of both virility and fertility, and gonadotropin withdrawal naturally leads to the failure of spermatogenesis[/U]. [U]This last statement is mainly due to the loss of testosterone production, as FSH is dispensable for male fertility, but LH is needed[/U] *Testosterone, and more specifically, intratesticular testosterone (ITT) levels are essential to male fertility *ITT and FSH are required to remain at consistently high levels to maintain normal spermatogenesis *A normal male’s ITT levels range between 400-600 ng/g while their serum levels are usually almost 100x lower *All in all, the Leydig cell acts as a vital mediator between the HPG axis and the effect of androgens on fertility, hence leading to the intratesticular environment necessary to conserve both fertility and virility *Although significant, [U]FSH alone cannot complete the necessary cycle of spermatogenesis[/U].[/B] [B]Similarly, even though an absence of FSH may lead to spermatogenic impairment, [U]decreased levels of ITT would completely abolish spermatogenesis[/U]. 17-OHP is an intermediate steroid synthesized within the adrenal gland zona fasciculata and the testes. 70% of the circulating 17-OHP is derived from the testes and the rest is thought to originate from the adrenal gland *Similar to testosterone, 17-OHP is also regulated by the HPG axis and undergoes diurnal variation mirroring testosterone, with peaks in the morning and falls by the evening to 60% of its original high point *INSL3 is a peptide hormone synthesized in adult Leydig cells and has been previously shown to be able to act as a biomarker for Leydig cell functionality *Inhibin B is a dimeric glycoprotein whose bioactivity is dependent on its dimerization of its respective α and βB subunits. Its function is representative of Sertoli cells, acting as a negative regulator to pituitary FSH *Standard ITT was found to be around 170 times higher than serum testosterone and did not correlate with serum LH, FSH, testosterone, DHT (dihydrotestosterone), or estradiol *DHT was found to be only 11 times higher within the testes than in the serum, likely due to the fact that most of it is made by the conversion of 5-alpha reductase in peripheral tissue [49] ([U]most of which is concentrated to the prostate with minimal expression in genital skin[/U]), as further shown in Fig. 2 [/B][/I] [/QUOTE]
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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone and Men's Health Articles
Male infertility and intratesticular T - insight into novel serum biomarkers
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