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Testosterone Replacement, Low T, HCG, & Beyond
Blood Test Discussion
Understanding the Variations of LH, FSH, and Testosterone: Implications for Diagnostic Accuracy
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<blockquote data-quote="madman" data-source="post: 276642" data-attributes="member: 13851"><p><strong>Take Home Points</strong></p><p></p><p></p><p><em><strong>*Notably, reproductive hormones vary during the day because of <u>diurnal rhythm (2), pulsatile secretion (3), and nutrient intake (4)</u>, which has significant implications for the diagnostic accuracy of reproductive hormones</strong></em></p><p></p><p><strong>*</strong><em><strong>Many hormones exhibit <u>both basal tonic secretion and pulsatile release</u> (3, 5).</strong></em></p><p></p><p><strong>*</strong><em><strong>Luteinizing hormone pulses typically have a <u>duration of 60–90 minutes</u> (6), and thus a single LH level will vary depending on the time point during the pulse cycle at which the measure is taken</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*<em><strong>Increased GnRH pulse frequency favors <u>LH-predominant secretion</u>, whereas reduced GnRH pulse frequency favors <u>follicle-stimulating hormone (FSH)-predominant secretion</u>. Therefore, a single LH and FSH level could vary with the number of pulses during the day; </strong></em></strong></em></p><p><em><strong><em><strong></strong></em></strong></em></p><p><em><strong><em><strong>*<em><strong>For the diagnosis of male hypogonadism, morning testosterone levels are recommended because <u>testosterone is recognized to have diurnal variation, with levels peaking between 05:30 and 08.00 hours and reaching a nadir from approximately 5:30 PM to 8:00 PM</u> (2)</strong></em></strong></em></strong></em></p><p><em><strong><em><strong></strong></em></strong></em></p><p><em><strong><em><strong>*<em><strong>Further, it is recommended to measure testosterone levels in the fasted state (1)<u> because feeding can decrease serum testosterone concentrations for >2 hours</u> (9, 10).</strong></em></strong></em></strong></em></p><p></p><p><strong>*</strong><em><strong><u>The initial morning value of reproductive hormone levels was typically higher than the mean value throughout the day</u> (percentage decrease from initial morning measure to daily mean: luteinizing hormone level 18.4%, follicle-stimulating hormone level 9.7%, testosterone level 9.2%, and estradiol level 2.1%)</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*<em><strong><u>Luteinizing hormone level was the most variable (CV 28%)</u>, followed by sex-steroid hormone levels (testosterone level 12% and estradiol level 13%), whereas follicle-stimulating hormone level was the least variable reproductive hormone (CV 8%)</strong></em></strong></em></p><p></p><p><strong>*</strong><em><strong> In healthy men, <u>testosterone levels fell between 9:00 AM and 5:00 PM by 14.9% (95% confidence interval 4.2, 25.5%)</u>, although morning levels correlated with (and could be predicted from) late afternoon levels in the same individual (r2 = 0.53, P<.0001)</strong></em></p><p><em><strong></strong></em></p><p><em><strong>*<em><strong><u>Testosterone levels were reduced more after a mixed meal (by 34.3%)</u> than during ad libitum feeding (9.5%), after an oral glucose load (6.0%), or an intravenous glucose load (7.4%)</strong></em></strong></em></p></blockquote><p></p>
[QUOTE="madman, post: 276642, member: 13851"] [B]Take Home Points[/B] [I][B]*Notably, reproductive hormones vary during the day because of [U]diurnal rhythm (2), pulsatile secretion (3), and nutrient intake (4)[/U], which has significant implications for the diagnostic accuracy of reproductive hormones[/B][/I] [B]*[/B][I][B]Many hormones exhibit [U]both basal tonic secretion and pulsatile release[/U] (3, 5).[/B][/I] [B]*[/B][I][B]Luteinizing hormone pulses typically have a [U]duration of 60–90 minutes[/U] (6), and thus a single LH level will vary depending on the time point during the pulse cycle at which the measure is taken *[I][B]Increased GnRH pulse frequency favors [U]LH-predominant secretion[/U], whereas reduced GnRH pulse frequency favors [U]follicle-stimulating hormone (FSH)-predominant secretion[/U]. Therefore, a single LH and FSH level could vary with the number of pulses during the day; *[I][B]For the diagnosis of male hypogonadism, morning testosterone levels are recommended because [U]testosterone is recognized to have diurnal variation, with levels peaking between 05:30 and 08.00 hours and reaching a nadir from approximately 5:30 PM to 8:00 PM[/U] (2)[/B][/I] *[I][B]Further, it is recommended to measure testosterone levels in the fasted state (1)[U] because feeding can decrease serum testosterone concentrations for >2 hours[/U] (9, 10).[/B][/I][/B][/I][/B][/I] [B]*[/B][I][B][U]The initial morning value of reproductive hormone levels was typically higher than the mean value throughout the day[/U] (percentage decrease from initial morning measure to daily mean: luteinizing hormone level 18.4%, follicle-stimulating hormone level 9.7%, testosterone level 9.2%, and estradiol level 2.1%) *[I][B][U]Luteinizing hormone level was the most variable (CV 28%)[/U], followed by sex-steroid hormone levels (testosterone level 12% and estradiol level 13%), whereas follicle-stimulating hormone level was the least variable reproductive hormone (CV 8%)[/B][/I][/B][/I] [B]*[/B][I][B] In healthy men, [U]testosterone levels fell between 9:00 AM and 5:00 PM by 14.9% (95% confidence interval 4.2, 25.5%)[/U], although morning levels correlated with (and could be predicted from) late afternoon levels in the same individual (r2 = 0.53, P<.0001) *[I][B][U]Testosterone levels were reduced more after a mixed meal (by 34.3%)[/U] than during ad libitum feeding (9.5%), after an oral glucose load (6.0%), or an intravenous glucose load (7.4%)[/B][/I][/B][/I] [/QUOTE]
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Testosterone Replacement, Low T, HCG, & Beyond
Blood Test Discussion
Understanding the Variations of LH, FSH, and Testosterone: Implications for Diagnostic Accuracy
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