SpencerD6571
New Member
This is a quote from Leeman under the thread supra physiological FT. After watching the videos by Dr. Andrew Winge and the lecture by Dr. Keith Nichols I've had to reevaluate everything I thought I knew about testosterone and estradiol. The lecture by Dr. Nichols is probably the most informative I have ever seen on the topic of testosterone and estradiol. Like him or not you have to admire the amount of work that must've gone in to putting that lecture together. I would encourage everyone to watch it before commenting. I've watched it three times and I've learned something each time that I missed the time before. Statements that High estradiol is very risky and unhealthy is based on baseline observations in men not on testosterone that are unhealthy and overweight. Yes men that are obese and have a lot of visceral adiposity also have high estradiol, but the high estradiol does not cause the harm...it's the visceral adiposity and insulin resistance, etc.
This was the first time that I've seen the evidence that the normal estradiol range represents men with total testosterone levels less than 600 and does not apply to men with levels above 600 or men on testosterone. I would encourage everyone to watch the lecture and then have an intelligent conversation about the content. He challenges those that promote the use of aromatase inhibitors to just simply present the evidence showing that it is more beneficial than giving testosterone alone. Not baseline observations, but actual interventional studies. Even though many of you need to watch it just like I needed to watch it. Most of you will not take the time. Those that are truly interested in the science and physiology will watch it, which will then allow for an intelligent and informed conversation. Here is AI's summary of the lecture, which actually doesn't do it justice.:
Testosterone: Beliefs Verses Science
This presentation critically examines prevailing beliefs surrounding testosterone therapy, with particular emphasis on diagnostic thresholds, therapeutic target ranges, free testosterone interpretation, estradiol physiology, and the increasingly common practice of aromatase inhibitor use in men receiving testosterone therapy. The central thesis is that many commonly accepted clinical practices in testosterone management have been shaped less by randomized outcome evidence than by reference-range convention, extrapolation, repetition, and unvalidated assumptions. The presentation argues for a return to physiology and clinical outcomes rather than rigid adherence to population-derived laboratory thresholds.
A major theme is the documented secular decline in male testosterone levels over recent decades. Multiple population studies from the United States, Denmark, Finland, Israel, NHANES, and large meta-analytic datasets are presented to show age-independent declines in serum testosterone that are not fully explained by obesity or lifestyle factors alone. The clinical implication is that modern laboratory reference ranges may increasingly reflect a population with declining androgen production rather than an ideal standard of male physiology. Consequently, downward shifts in “normal” testosterone ranges risk normalizing pathology and may contribute to underdiagnosis and undertreatment of symptomatic men.
The presentation challenges the use of a single serum testosterone threshold to define testosterone deficiency. It emphasizes that androgen status is not determined by total testosterone alone, but by a combination of absolute testosterone concentration, magnitude of decline from an individual’s prior baseline, SHBG-mediated free testosterone availability, androgen receptor sensitivity, tissue responsiveness, and downstream post-receptor signaling. The discussion of CAG repeat length in the androgen receptor gene is used as a mechanistic example of why two men with the same serum testosterone may experience different biological androgen effects. In this framework, testosterone thresholds are population statistics, not individualized physiology.
Free testosterone is presented as a more clinically relevant marker than total testosterone in many symptomatic men, particularly when SHBG varies substantially. The deck highlights the lack of harmonized free testosterone reference ranges and the wide discrepancy between commercial laboratory ranges, especially Quest and LabCorp. Data from healthy non-obese men measured by equilibrium dialysis are used to argue that commonly used laboratory lower limits may be too low and may fail to identify clinically meaningful androgen deficiency. The presentation therefore favors direct free testosterone measurement by equilibrium dialysis and interpretation in the context of symptoms, physiology, and treatment response.
The treatment-target discussion argues that aiming exclusively for low-to-mid normal testosterone concentrations is not strongly supported by dose-response evidence. Several randomized trials are reviewed to show that increases in lean body mass, reductions in fat mass, muscle size, strength, and related metabolic outcomes often occur in a graded fashion as testosterone exposure rises. The presentation distinguishes between testosterone’s relatively linear anabolic effects in skeletal muscle and its more threshold-dependent, saturable effects in tissues such as the central nervous system. This distinction is used to explain why higher testosterone levels may continue to improve body composition and performance-related outcomes even after mood, libido, cognition, and general well-being have plateaued.
Estradiol is the dominant focus of the latter half of the presentation. The deck argues that estradiol in men should not be treated merely as an adverse byproduct of testosterone therapy, but as an essential active metabolite required for normal male physiology. Testosterone is framed as a “three-hormone” system: testosterone itself, dihydrotestosterone, and estradiol. The presentation emphasizes that estradiol contributes to bone health, vascular function, insulin sensitivity, fat-mass regulation, sexual desire, erectile physiology, cognition, and other outcomes. It repeatedly notes that the major randomized trials demonstrating testosterone benefits generally preserved physiologic aromatization rather than suppressing estradiol.
A central physiological argument is that serum estradiol is an imperfect surrogate for tissue-level estrogen signaling in men. The presentation distinguishes endocrine, paracrine, autocrine, and intracrine hormone action, emphasizing that much estradiol activity in men occurs locally within tissues such as brain, bone, adipose tissue, vascular endothelium, and sexual-function pathways. In that model, serum estradiol represents spillover from local production rather than a direct measurement of tissue estrogen receptor activation. This undermines the practice of using a fixed serum estradiol number as a universal therapeutic target.
The presentation also critiques the standard male estradiol reference range, particularly the commonly cited LabCorp range of approximately 8–35 pg/mL. It argues that this range was derived from men not receiving testosterone therapy, likely with average testosterone levels below 600 ng/dL, and should not automatically be applied to men whose testosterone levels are therapeutically raised above that range. The deck therefore challenges the assumption that estradiol above the commercial laboratory range is intrinsically pathologic in men receiving testosterone therapy.
Aromatase inhibitor use is presented as the key example of physiology being disrupted without adequate outcome evidence. The presentation reviews trials in which aromatase inhibition attenuated benefits of testosterone, particularly on fat mass, insulin sensitivity, sexual function, and body composition. By contrast, 5-alpha-reductase inhibition is discussed as showing that DHT is not essential for testosterone’s anabolic effects in skeletal muscle, whereas estradiol appears to be necessary for many metabolic, sexual, and body-composition benefits. The conclusion is that blocking estradiol during testosterone therapy risks impairing the very outcomes testosterone therapy is intended to produce.
The presentation strongly critiques the “estradiol sweet spot” concept. It argues that the claim rests on two unsupported assumptions: first, that serum estradiol accurately reflects tissue estrogen biology; and second, that partial suppression of estradiol produces superior outcomes compared with intact testosterone–estradiol coupling. The deck argues that full estradiol suppression clearly attenuates benefit, while partial suppression should be understood as partial attenuation, not proven optimization. In publication language, the “sweet spot” is framed as an unvalidated clinical hypothesis rather than an evidence-based target.
The deck also addresses commonly cited concerns that elevated estradiol causes erectile dysfunction, libido problems, gynecomastia, acne, hypertension, cancer, or nonspecific “high estrogen symptoms.” Observational studies linking higher estradiol to sexual dysfunction are critiqued for confounding by age, obesity, comorbidity burden, vascular disease, metabolic dysfunction, medication use, and weak estradiol measurement methods. The presentation argues that these studies are hypothesis-generating but cannot justify aromatase inhibitor use in men on testosterone therapy. Similarly, acne is attributed primarily to androgenic stimulation of sebaceous glands, not estradiol, and gynecomastia is presented as uncommon and better managed selectively rather than prevented with routine aromatase inhibition.
A notable section proposes that sexual dysfunction experienced by a small subset of men after initiating testosterone therapy is more plausibly mediated by serotonergic mechanisms than by estradiol excess. Testosterone, through central mechanisms that may involve local aromatization to estradiol, can increase serotonergic tone. In susceptible individuals with high baseline serotonergic activity, this may cross a threshold that produces symptoms resembling SSRI-associated sexual dysfunction, including reduced libido, erectile difficulty, genital sensory change, delayed ejaculation, or anorgasmia. The proposed management strategy favors time, dose reduction, or symptom-specific pharmacologic treatment rather than routine estradiol suppression.
The presentation’s guideline review concludes that no major testosterone therapy guideline recommends routine estradiol measurement or routine estradiol suppression in all men receiving testosterone therapy. The AUA and CUA support estradiol measurement mainly in men with breast symptoms or gynecomastia, and the AUA also recommends measurement in men receiving aromatase inhibitors. Other major guidelines do not mandate routine estradiol testing or control. This is used to rebut the claim that routine estradiol monitoring is guideline-required.
The final argument is a burden-of-proof framework. Because the clinical benefits of testosterone therapy were demonstrated largely under conditions of preserved aromatization, those advocating routine estradiol suppression are altering the physiology under which benefit was established. Therefore, the presentation argues that the evidentiary burden rests on aromatase inhibitor proponents to demonstrate that testosterone plus estradiol suppression produces superior patient-important outcomes compared with testosterone therapy alone. In the absence of such randomized outcome evidence, routine aromatase inhibition is characterized as physiologic interference rather than evidence-based optimization.
This was the first time that I've seen the evidence that the normal estradiol range represents men with total testosterone levels less than 600 and does not apply to men with levels above 600 or men on testosterone. I would encourage everyone to watch the lecture and then have an intelligent conversation about the content. He challenges those that promote the use of aromatase inhibitors to just simply present the evidence showing that it is more beneficial than giving testosterone alone. Not baseline observations, but actual interventional studies. Even though many of you need to watch it just like I needed to watch it. Most of you will not take the time. Those that are truly interested in the science and physiology will watch it, which will then allow for an intelligent and informed conversation. Here is AI's summary of the lecture, which actually doesn't do it justice.:
Testosterone: Beliefs Verses Science
This presentation critically examines prevailing beliefs surrounding testosterone therapy, with particular emphasis on diagnostic thresholds, therapeutic target ranges, free testosterone interpretation, estradiol physiology, and the increasingly common practice of aromatase inhibitor use in men receiving testosterone therapy. The central thesis is that many commonly accepted clinical practices in testosterone management have been shaped less by randomized outcome evidence than by reference-range convention, extrapolation, repetition, and unvalidated assumptions. The presentation argues for a return to physiology and clinical outcomes rather than rigid adherence to population-derived laboratory thresholds.
A major theme is the documented secular decline in male testosterone levels over recent decades. Multiple population studies from the United States, Denmark, Finland, Israel, NHANES, and large meta-analytic datasets are presented to show age-independent declines in serum testosterone that are not fully explained by obesity or lifestyle factors alone. The clinical implication is that modern laboratory reference ranges may increasingly reflect a population with declining androgen production rather than an ideal standard of male physiology. Consequently, downward shifts in “normal” testosterone ranges risk normalizing pathology and may contribute to underdiagnosis and undertreatment of symptomatic men.
The presentation challenges the use of a single serum testosterone threshold to define testosterone deficiency. It emphasizes that androgen status is not determined by total testosterone alone, but by a combination of absolute testosterone concentration, magnitude of decline from an individual’s prior baseline, SHBG-mediated free testosterone availability, androgen receptor sensitivity, tissue responsiveness, and downstream post-receptor signaling. The discussion of CAG repeat length in the androgen receptor gene is used as a mechanistic example of why two men with the same serum testosterone may experience different biological androgen effects. In this framework, testosterone thresholds are population statistics, not individualized physiology.
Free testosterone is presented as a more clinically relevant marker than total testosterone in many symptomatic men, particularly when SHBG varies substantially. The deck highlights the lack of harmonized free testosterone reference ranges and the wide discrepancy between commercial laboratory ranges, especially Quest and LabCorp. Data from healthy non-obese men measured by equilibrium dialysis are used to argue that commonly used laboratory lower limits may be too low and may fail to identify clinically meaningful androgen deficiency. The presentation therefore favors direct free testosterone measurement by equilibrium dialysis and interpretation in the context of symptoms, physiology, and treatment response.
The treatment-target discussion argues that aiming exclusively for low-to-mid normal testosterone concentrations is not strongly supported by dose-response evidence. Several randomized trials are reviewed to show that increases in lean body mass, reductions in fat mass, muscle size, strength, and related metabolic outcomes often occur in a graded fashion as testosterone exposure rises. The presentation distinguishes between testosterone’s relatively linear anabolic effects in skeletal muscle and its more threshold-dependent, saturable effects in tissues such as the central nervous system. This distinction is used to explain why higher testosterone levels may continue to improve body composition and performance-related outcomes even after mood, libido, cognition, and general well-being have plateaued.
Estradiol is the dominant focus of the latter half of the presentation. The deck argues that estradiol in men should not be treated merely as an adverse byproduct of testosterone therapy, but as an essential active metabolite required for normal male physiology. Testosterone is framed as a “three-hormone” system: testosterone itself, dihydrotestosterone, and estradiol. The presentation emphasizes that estradiol contributes to bone health, vascular function, insulin sensitivity, fat-mass regulation, sexual desire, erectile physiology, cognition, and other outcomes. It repeatedly notes that the major randomized trials demonstrating testosterone benefits generally preserved physiologic aromatization rather than suppressing estradiol.
A central physiological argument is that serum estradiol is an imperfect surrogate for tissue-level estrogen signaling in men. The presentation distinguishes endocrine, paracrine, autocrine, and intracrine hormone action, emphasizing that much estradiol activity in men occurs locally within tissues such as brain, bone, adipose tissue, vascular endothelium, and sexual-function pathways. In that model, serum estradiol represents spillover from local production rather than a direct measurement of tissue estrogen receptor activation. This undermines the practice of using a fixed serum estradiol number as a universal therapeutic target.
The presentation also critiques the standard male estradiol reference range, particularly the commonly cited LabCorp range of approximately 8–35 pg/mL. It argues that this range was derived from men not receiving testosterone therapy, likely with average testosterone levels below 600 ng/dL, and should not automatically be applied to men whose testosterone levels are therapeutically raised above that range. The deck therefore challenges the assumption that estradiol above the commercial laboratory range is intrinsically pathologic in men receiving testosterone therapy.
Aromatase inhibitor use is presented as the key example of physiology being disrupted without adequate outcome evidence. The presentation reviews trials in which aromatase inhibition attenuated benefits of testosterone, particularly on fat mass, insulin sensitivity, sexual function, and body composition. By contrast, 5-alpha-reductase inhibition is discussed as showing that DHT is not essential for testosterone’s anabolic effects in skeletal muscle, whereas estradiol appears to be necessary for many metabolic, sexual, and body-composition benefits. The conclusion is that blocking estradiol during testosterone therapy risks impairing the very outcomes testosterone therapy is intended to produce.
The presentation strongly critiques the “estradiol sweet spot” concept. It argues that the claim rests on two unsupported assumptions: first, that serum estradiol accurately reflects tissue estrogen biology; and second, that partial suppression of estradiol produces superior outcomes compared with intact testosterone–estradiol coupling. The deck argues that full estradiol suppression clearly attenuates benefit, while partial suppression should be understood as partial attenuation, not proven optimization. In publication language, the “sweet spot” is framed as an unvalidated clinical hypothesis rather than an evidence-based target.
The deck also addresses commonly cited concerns that elevated estradiol causes erectile dysfunction, libido problems, gynecomastia, acne, hypertension, cancer, or nonspecific “high estrogen symptoms.” Observational studies linking higher estradiol to sexual dysfunction are critiqued for confounding by age, obesity, comorbidity burden, vascular disease, metabolic dysfunction, medication use, and weak estradiol measurement methods. The presentation argues that these studies are hypothesis-generating but cannot justify aromatase inhibitor use in men on testosterone therapy. Similarly, acne is attributed primarily to androgenic stimulation of sebaceous glands, not estradiol, and gynecomastia is presented as uncommon and better managed selectively rather than prevented with routine aromatase inhibition.
A notable section proposes that sexual dysfunction experienced by a small subset of men after initiating testosterone therapy is more plausibly mediated by serotonergic mechanisms than by estradiol excess. Testosterone, through central mechanisms that may involve local aromatization to estradiol, can increase serotonergic tone. In susceptible individuals with high baseline serotonergic activity, this may cross a threshold that produces symptoms resembling SSRI-associated sexual dysfunction, including reduced libido, erectile difficulty, genital sensory change, delayed ejaculation, or anorgasmia. The proposed management strategy favors time, dose reduction, or symptom-specific pharmacologic treatment rather than routine estradiol suppression.
The presentation’s guideline review concludes that no major testosterone therapy guideline recommends routine estradiol measurement or routine estradiol suppression in all men receiving testosterone therapy. The AUA and CUA support estradiol measurement mainly in men with breast symptoms or gynecomastia, and the AUA also recommends measurement in men receiving aromatase inhibitors. Other major guidelines do not mandate routine estradiol testing or control. This is used to rebut the claim that routine estradiol monitoring is guideline-required.
The final argument is a burden-of-proof framework. Because the clinical benefits of testosterone therapy were demonstrated largely under conditions of preserved aromatization, those advocating routine estradiol suppression are altering the physiology under which benefit was established. Therefore, the presentation argues that the evidentiary burden rests on aromatase inhibitor proponents to demonstrate that testosterone plus estradiol suppression produces superior patient-important outcomes compared with testosterone therapy alone. In the absence of such randomized outcome evidence, routine aromatase inhibition is characterized as physiologic interference rather than evidence-based optimization.
