Are average testosterone levels in men actually decreasing, and what are the primary reasons?

There is convincing evidence, from cohort studies and NHANES data, that average testosterone levels have declined in men across different age groups over time. While chemical exposure is a possible cause, increased rates of obesity and a more sedentary lifestyle are significant contributors, as fat tissue aromatizes testosterone into estrogen, and heat from insulating fat can reduce production efficiency.

Does carrying a cell phone in your pocket negatively impact sperm quality or testosterone levels?

Current data on cell phone exposure and its impact on sperm health or testosterone levels are not convincing for a clinically meaningful change. While some in vitro studies suggest a slight increase in sperm DNA fragmentation with close proximity to a cell phone, the evidence is not strong enough to recommend specific actions beyond general awareness.

What lifestyle factors should men avoid or adopt to improve sperm quality and maintain healthy testosterone?

To improve sperm quality, men should avoid heat exposure to the scrotum (e.g., hot tubs, prolonged use of seat warmers). For both testosterone and sperm health, maintaining overall physical fitness, a healthy body weight, and not smoking are crucial. Moderate alcohol consumption beyond 20 drinks a week might have negative effects, and some studies link daily cannabis use to lower sperm concentration, motility, and morphology.

Is testosterone therapy (exogenous testosterone) safe for long-term use, and does it increase prostate cancer risk?

Testosterone therapy does not appear to increase the risk of prostate cancer. The theory of 'saturation' suggests that once prostate testosterone receptors are filled (at a fairly low level), additional testosterone does not further stimulate prostate growth or cancer risk. However, reproductive-age men need to be aware that testosterone therapy can significantly lower sperm production and should consider sperm cryopreservation if fertility is desired.

How does sleep duration affect male reproductive health?

Sleep duration has a U-shaped relationship with semen quality, meaning both too little and too much sleep can be detrimental. The ideal range for semen quality and broad testicular function is typically 7 to 9 hours of sleep per night. Men getting less or more than this range tend to have lower semen quality.

What is the significance of semen quality as a broader marker of male health?

Semen quality is considered an excellent marker for overall male health, often referred to as the 'sixth vital sign.' Studies show men with more health problems tend to have lower semen quality, and higher semen quality is associated with increased longevity, fewer doctor visits, and lower cancer rates. This link is thought to stem from shared genetic pathways and early developmental influences.

What are the risks associated with paternal age for offspring, such as autism or other conditions?

Older paternal age is linked to increased risks for several conditions in offspring, including autism, bipolar disorder, schizophrenia, dwarfism (achondroplasia), and certain cancers (breast, prostate, leukemia, CNS cancers). Each year, approximately two mutations are generated in sperm DNA, and these can accumulate with age, leading to epigenetic changes and potential neurocognitive developmental effects in children.

What are the most common causes of erectile dysfunction, and how is it typically treated?

Most erectile dysfunction is organic, not hormonal, stemming primarily from blood flow issues (vascular problems). Common causes include high blood pressure, diabetes, atherosclerosis, and pelvic cancer treatments. First-line treatments usually involve oral phosphodiesterase inhibitors like sildenafil (Viagra) or tadalafil (Cialis), which help 60-70% of men. These treatments address the symptoms but lifestyle factors and underlying vascular health should also be managed.

What is Post-Finasteride Syndrome, and what are its implications?

Post-Finasteride Syndrome is a condition where men experience persistent sexual dysfunction (low libido, erectile dysfunction) and other issues even after discontinuing drugs like finasteride or dutasteride, which are used to treat hair loss. While some men recover, for a handful, these effects can be seemingly permanent and treatment-refractory, with mechanisms still largely unknown.

What is clomiphene, and how is it used in male reproductive health?

Clomiphene is a selective estrogen receptor modulator (SERM) that blocks estrogen's feedback on the hypothalamus and pituitary, leading to increased production of LH and FSH. This results in higher natural testosterone production and can stimulate sperm production without the toxicity to sperm count seen with exogenous testosterone. It's used for reproductive-age men with symptomatic low testosterone who wish to maintain fertility.

What are varicocele and Peyronie's disease, and how are they managed?

Varicocele is a common condition of dilated veins in the scrotum, affecting 15% of men and causing 30-40% of male infertility, often treated surgically. Peyronie's disease is penile scarring causing curvature or deformity, affecting 5-10% of men, and is treated with medications like collagenase (Xiaflex) to dissolve scar tissue, stretching devices, or surgery.

Should men perform regular testicular self-exams?

While national guidelines recommend against regular testicular self-exams due to concerns about anxiety outweighing actual cancer diagnoses, Dr. Eisenberg encourages men to be aware of their bodies. If a man identifies a firm, painless mass on his testicle, he should seek medical attention, as no one knows their scrotum better than they do.

Why is it important for men to get a sperm analysis, even if they're not currently trying to conceive?

A sperm analysis is a valuable early health indicator, and more information is always better. It can reveal reproductive potential and serve as a barometer for overall health, with studies linking lower sperm quality to increased risks of heart disease, diabetes, and mortality. Many men are unaware of low or absent sperm counts, which can only be identified through a formal test.

Key Moments

Improving Male Sexual Health, Function & Fertility | Dr. Michael Eisenberg

Andrew Huberman

Science & Technology7 min read158 min video

Nov 6, 2023|692,388 views|13,053|808

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TL;DR

Improving male sexual health involves addressing diet, exercise, sleep, substance use, and considering medical evaluations.

Key Insights

Semen quality and testosterone levels appear to be declining over time, influenced by environmental factors, obesity, and lifestyle.

Erectile dysfunction is predominantly caused by vascular issues (blood flow) and neural factors, with less than 10% stemming from hormonal imbalances.

Testosterone therapy, while effective for low testosterone, can significantly suppress sperm production and may lead to lasting issues (Post-Finasteride Syndrome), especially when used for augmentation.

Lifestyle factors like adequate sleep (7-9 hours), regular exercise, maintaining a healthy weight, and avoiding smoking/excessive alcohol are crucial for male reproductive health.

Paternal age (over 40) is linked to increased risks for offspring, including neurodevelopmental conditions and certain cancers, due to accumulated genetic mutations.

Routine screenings for sperm quality and hormone levels are recommended for all men as early health barometers, similar to blood pressure and lipid checks.

THE DECLINE OF SPERM QUALITY AND TESTOSTERONE

There's an ongoing debate regarding the global decline in male sperm quality and testosterone levels. While some studies support this decline, the exact reasons remain controversial. Hypotheses include environmental chemical exposures (e.g., phthalates, BPA), obesity, and sedentary lifestyles. Obesity is a significant factor as fat tissue converts testosterone to estrogen, lowering circulating testosterone, and can also insulate the testicles, affecting sperm production efficiency. Sperm quality is measured by semen volume, sperm count, motility (movement), and morphology (shape), with advanced tests for DNA fragmentation and epigenetic profiles.

THE COMPLICATED RELATIONSHIP WITH SPERM QUALITY

Sperm quality is a crucial yet often overlooked aspect of fertility, with men contributing to approximately half of all infertility cases. The ability to achieve pregnancy through IVF using a single sperm has perhaps reduced the focus on male fertility research. While instruments for measuring sperm quality are more advanced, this refinement alone doesn't entirely explain the observed decline. Geographic variations in semen quality suggest influences from genetics, diet, exercise, and lifestyle factors. Longitudinal studies are needed to definitively track changes over time and rule out evolutionary or methodological biases.

LIFESTYLE FACTORS AND THEIR IMPACT ON MALE REPRODUCTIVE HEALTH

Heat negatively impacts sperm production, making activities like prolonged hot tub use potentially detrimental. While saunas offer health benefits, cooling the scrotal area during extended sauna sessions is advised to protect sperm. The impact of cell phone proximity to the testicles on sperm health and testosterone is not conclusively proven, but some studies suggest potential minor DNA fragmentation. However, factors like smoking, excessive alcohol (over 20 drinks/week), and drug use (e.g., cannabis, opioids) are strongly linked to lower sperm quality and should be avoided or significantly reduced. Genetic variations in alcohol metabolism may increase sensitivity to alcohol's negative effects.

THE MYTHS AND REALITIES OF TESTOSTERONE THERAPY

Testosterone levels generally peak in early 20s and decline by about 1% annually. However, significant individual variation exists, with some older men maintaining very high levels, indicating complex genetic and physiological factors at play. Exogenous testosterone therapy (often mislabeled TRT) can dramatically reduce endogenous testosterone production and sperm count by suppressing the pituitary's release of LH and FSH. Approximately 5% of infertile men are infertile due to testosterone therapy. HCG (human chorionic gonadotropin) and FSH injections can help maintain sperm production if men wish to conceive while on testosterone, but FSH is often prohibitively expensive.

ADDRESSING ERECTILE DYSFUNCTION

Erectile dysfunction (ED) is common, affecting over half of men over 40. Contrary to popular belief, less than 10% of ED cases are due to hormonal imbalances. The vast majority stem from organic causes, primarily vascular issues (blood flow problems) and neural factors, often linked to conditions like high blood pressure, diabetes, and atherosclerosis. ED can be an early marker for broader vascular disease. First-line treatments include oral phosphodiesterase inhibitors (e.g., Viagra, Cialis), which are effective in 60-70% of men. If these fail, urethral suppositories, penile injections, and in severe cases, penile implants (bendable or inflatable) are available, offering effective solutions for almost all men.

THE IMPORTANCE OF SLEEP AND EXERCISE

Adequate, quality sleep (7-9 hours per night) is vital for male reproductive health. Both insufficient and excessive sleep are associated with lower semen quality, exhibiting a U-shaped relationship. Regular physical activity, characterized by higher step counts, is linked to higher testosterone levels, independent of body weight, emphasizing the broader health benefits of being active. Cycling, particularly prolonged rides, can pose risks to sexual function and sperm quality due to heat and nerve/blood vessel compression from saddle pressure. Using specialized saddles and standing up on the pedals can mitigate these risks. Over-the-counter medications like NSAIDs are generally considered safe for male reproductive health.

CANNABIS, DRUGS, AND TESTICULAR DISORDERS

Cannabis use, especially daily, has been linked to lower sperm concentration, motility, and morphology in some studies. However, the data are not entirely consistent, possibly due to variations in cannabis composition, frequency of use, and delivery method. Opioids and other illicit drugs are generally considered detrimental to reproductive health, though comprehensive studies are limited. Varicoceles, dilated veins in the scrotum affecting 15% of men, are a common cause of infertility (30-40% of cases) and can cause discomfort or stunted testicular growth by warming the testicles and hindering metabolite clearance. Peyronie's disease, a scarring of the penis causing curvature or deformity, affects 5-10% of men and can be treated with medication, stretching devices, or surgery.

PROSTATE HEALTH: FUNCTION, MAINTENANCE, AND DISEASES

The prostate, a walnut-sized gland, plays a crucial role in reproduction by contributing to semen volume and sperm health. After reproductive years, it can become a source of issues as it naturally enlarges with age, constricting the urethra and causing urinary symptoms like frequent urination, weak stream, and incomplete emptying. Triggers for urinary symptoms include excessive fluid intake before bed, spicy/acidic foods, caffeine, and alcohol. Low-dose tadalafil (2.5-5mg daily) can alleviate urinary symptoms and improve erectile function by increasing blood flow to the prostate. While prostate cancer is androgen-mediated, testosterone therapy does not increase the risk of prostate cancer due to a 'saturation model' where existing receptors are already filled.

PELVIC FLOOR HEALTH AND UNUSUAL SYMPTOMS

Pelvic floor muscles support the base of the penis, prostate, bladder, and rectum, crucial for continence and ejaculation. Both weak and overly tense pelvic floors can cause urinary and sexual dysfunction. Pelvic floor physical therapy, which can include exercises like Kegels or relaxation techniques, is beneficial but should be tailored to individual needs. An uncommonly persistent split urine stream is an indicator of potential issues like urethral stricture or prostatic enlargement that warrant medical evaluation. Male urinary tract infections (UTIs) are rare due to the long urethra, and multiple occurrences should prompt evaluation for underlying anatomical issues.

THE PUZZLE OF PENILE LENGTH AND PATERNAL AGE RISKS

A recent meta-analysis of over 50,000 men found, surprisingly, that average erect penile length has increased over the past 30 years, defying expectations of decline. This rapid change suggests environmental or hormonal influences more than genetic shifts, possibly linked to earlier puberty or exposure to androgenic endocrine disruptors in utero. This contrasts with the declining sperm quality trend and highlights complex, often contradictory, environmental impacts on male reproductive development. Paternal age (over 40) is associated with increased risks for offspring, including conditions like achondroplasia and neurodevelopmental disorders such as autism and schizophrenia. This is attributed to accumulated germline mutations and epigenetic changes in sperm over time. Freezing sperm at a younger age is a reasonable mitigation strategy for those planning delayed fatherhood.

DHT BLOCKERS, POST-FINASTERIDE SYNDROME, AND CONCERNS

Drugs like finasteride and dutasteride, which block dihydrotestosterone (DHT) to treat hair loss and prostate enlargement, can cause sexual dysfunction, including low libido and erectile dysfunction. While some men experience symptom resolution upon discontinuation, a subset develops 'Post-Finasteride Syndrome,' characterized by persistent and sometimes permanent sexual and cognitive side effects. The exact mechanisms are not fully understood, but it highlights the unpredictable and potentially severe consequences of altering hormone pathways, especially in younger men using these drugs for cosmetic purposes. Men considering these medications must be aware of these serious risks.

PROLACTIN, ESTROGEN, AND TESTICULAR SELF-EXAMS

Hyperprolactinemia (elevated prolactin levels) is a less common diagnosis, but when present, can cause low testosterone, low libido, and very low sperm production, sometimes indicating a prolactin-secreting pituitary tumor. Elevated estrogen levels, often linked to obesity (due to aromatization of testosterone), can also cause problems like gynecomastia (male breast tissue). While national guidelines advise against routine testicular self-exams due to anxiety concerns, men should be vigilant about any changes or firm, painless lumps in their testicles, as early detection of testicular cancer is crucial.

ASSESSING MALE REPRODUCTIVE HEALTH: ACCESSIBILITY AND VALUE

Comprehensive assessment of male reproductive health, including hormone profiles (testosterone, estrogen, prolactin) and semen analyses, is crucial for overall well-being beyond just fertility. These metrics serve as 'barometers of health,' with lower sperm quality and testosterone levels correlated with higher risks of heart disease, diabetes, and mortality. Such evaluations can also uncover serious underlying medical conditions or even cancers. While historically expensive, innovations (e.g., at-home semen analysis kits) are making these tests more accessible. Men should discuss these screenings with their primary care physicians or urologists, as insurance coverage is improving.

Mentioned in This Episode

●Supplements

●Products

●Software & Apps

●Organizations

●Studies Cited

●Concepts

●People Referenced

Common Questions

There is a significant debate among experts about whether sperm quality is declining globally. Multiple meta-analyses, including recent ones, suggest a decline even across non-Western countries. Potential causes include environmental chemical exposures (like phthalates and BPA, especially in utero), and the global rise in obesity. However, some argue that improved measurement techniques over time could also create an appearance of decline.

Topics

Health & Longevity Human Performance Prostate Health Sperm Count Decline Medicine & Clinical Male Reproductive Health Testosterone Enclination Erectile Dysfunction Treatments Pelvic Floor Therapy Paternal Age Effects Hormone Therapy Risks

Mentioned in this video

People

Randy Nelson

Author of a textbook on behavioral endocrinology that includes a graph showing testosterone levels as a function of age in NHANES, indicating significant variation even in older men.

Michael Eisenberg

Medical doctor specializing in urology and an expert in male sexual function and fertility, clinician, and research scientist with over 300 peer-reviewed articles.

Arnold Kegel

Physician after whom Kegel exercises are named, which are pelvic floor strengthening exercises.

Drugs & Medications

acetaminophen

Non-steroidal anti-inflammatory drug (NSAID) which is currently thought to be safe and not negatively impact sperm quality or testosterone.

penile injections

A therapy involving injecting vasodilators directly into the erectile bodies of the penis, with 80-90% efficacy for achieving and maintaining erections. This is an on-demand treatment taught for self-administration.

Vardenafil

An oral phosphodiesterase inhibitor, a first-line treatment for erectile dysfunction, effective for 60-70% of men.

Sildenafil

An oral phosphodiesterase inhibitor, a first-line treatment for erectile dysfunction, effective for 60-70% of men. Also known by its brand name, Viagra.

varicocele

A common condition (15% of men) characterized by dilated veins in the scrotum, a leading cause of infertility (30-40% of cases). It is thought to warm the testicle and impair metabolite clearance, potentially leading to discomfort, low sperm counts, and testicular damage.

Avanafil

An oral phosphodiesterase inhibitor, a first-line treatment for erectile dysfunction, effective for 60-70% of men.

Collagenase

An FDA-approved medicine for Peyronie's disease that dissolves scar tissue, helping to reduce penile curvature.

Bisphenol A

A chemical that preclinical studies suggest may harm reproductive function in men and women.

Oxandrolone

A synthetic anabolic steroid with a structure closely mimicking dihydrotestosterone (DHT). Discussed in the context of a subculture of post-pubertal males attempting to increase penile length, but not recommended due to lack of physiological basis.

Clomiphene

A selective estrogen receptor modulator (SERM) that blocks estrogen receptors, leading to increased production of FSH and LH, thereby augmenting the body's own testosterone and potentially improving sperm production without the toxic effects of exogenous testosterone.

Human Chorionic Gonadotropin

A therapy used to stimulate sperm production in men taking testosterone therapy, typically at low doses (500-1000 units every other day); it is more cost-effective than FSH but less physiologically precise for sperm production.

Urethral Suppository

A vasodilator medication inserted into the tip of the penis, absorbed by the penal tissue to facilitate erections, used when oral therapies are not effective.

Finasteride

A 5-alpha-reductase inhibitor that suppresses dihydrotestosterone (DHT), used to treat hair loss and prostate issues. Can cause sexual dysfunction, low libido, and a persistent post-finasteride syndrome in some men.

Tadalafil

An oral phosphodiesterase inhibitor, a first-line treatment for erectile dysfunction, effective for 60-70% of men. Known for its longer half-life (around 20 hours), often marketed as a 'weekend pill'. Also available in low daily doses (2.5-5mg) to help with urinary symptoms and erectile function.

Dutasteride

Peyronie's disease

A condition characterized by scarring of the penis leading to curvature or deformity during erections, affecting 5-10% of men. It can result from injury or surgery and causes psychological bother and physical difficulty during sex. Treatments include collagenase (Xiaflex), stretching devices, and surgery.

Concepts

MRI

Imaging technique used in one study to show that children born to older fathers had slightly smaller brains just after birth.

Hypospadias

A birth condition where the urethral meatus is not at the tip of the penis but along the proximal urethra or further down, typically affecting about 1% of births and usually surgically corrected.

Phthalates

Chemicals mentioned in preclinical studies that may harm reproductive function in men and women, especially during in utero development.

Barker Hypothesis

Hypothesis suggesting that gestational effects, such as premature birth, can have prolonged impacts on health, including reproductive function and increased risk of cardiovascular disease.

Intracytoplasmic Sperm Injection

A technique used in IVF where a single sperm is injected into an egg, drastically reducing the number of functional sperm required for conception.

ALDH2 gene

Gene where a mutation is common in some East Asian cultures (40-50% Chinese/Taiwanese), leading to flushing and potentially higher risk when consuming alcohol due to impaired alcohol metabolism.

Leydig cells

Cells in the testes that are stimulated by Luteinizing Hormone (LH) to produce testosterone.

dihydrotestosterone

A hormone important for male embryonic development of penile tissue and subsequent growth during puberty. It causes miniaturization of hair follicles but also growth of beard hair. Its suppression can lead to sexual dysfunction.

Alcohol Dehydrogenase

Enzyme involved in alcohol metabolism; a mutation in the ALDH2 gene, common in East Asian populations, leads to flushing and potentially higher risk from alcohol consumption due to reduced metabolism of toxic alcohol forms.

Follicle-stimulating hormone

Hormone produced by the pituitary gland that stimulates sperm production in the testes.

Luteinizing Hormone

Hormone produced by the pituitary gland that stimulates Leydig cells in the testes to make testosterone.

Autism

Neurosychiatric condition with a small but statistically significant increased risk in offspring of fathers older than 40.

Achondroplasia

A condition first noticed to be more common in last-born children, later linked to paternal age and a mutation in the fibroblast growth factor receptor.

Selfish spermatogonial selection

A hypothesis suggesting that some mutations occurring randomly in proliferation pathways give sperm containing them an advantage, making them more likely to lead to a child and explaining the discrepancy between expected and observed mutation rates.

Post-Finasteride Syndrome

A syndrome characterized by persistent sexual dysfunction and other issues even after discontinuing finasteride or dutasteride, affecting a subset of men and appearing to be permanent in some cases.

prolactin

Hormone that, when elevated (hyperprolactinemia), can lead to low testosterone, very low sperm production, and is sometimes indicative of a prolactin-secreting tumor.

Pituitary Gland

Gland that receives signals from the brain and releases critical hormones (LH and FSH) controlling testosterone and sperm production from the testes.

Nocturnal penile tumescence

Normal, involuntary erections that occur during sleep, particularly during REM sleep stages, indicating healthy erectile function.

Fibroblast Growth Factor Receptor

The mutation in this receptor is responsible for Achondroplasia, which is more common in offspring of older fathers.

In-vitro fertilization

A powerful infertility treatment where sperm and egg are mixed in a dish to create life, lowering the bar for necessary sperm count due to techniques like ICSI.

Products

Penile Implants

Surgical devices implanted inside the penis to allow men to achieve a rigid erection, available in non-inflatable (bendable rod) and inflatable (pump in scrotum) forms, used for severe erectile dysfunction.

Supplements

Vitamin D3

Mentioned as part of a bonus offer with AG1, crucial for overall health.

Ibuprofen

Non-steroidal anti-inflammatory drug (NSAID) which is currently thought to be safe and not negatively impact sperm quality or testosterone.

Element

An electrolyte drink containing sodium, magnesium, and potassium, without sugar, used to support cellular and nerve function, especially during physical activity or sauna use.

Vitamin K2

Mentioned as part of a bonus offer with AG1, crucial for overall health.

Organizations

World Health Organization

International organization that periodically reviews literature and defines cut-off points for normal versus subfertile semen parameters.

National Health and Nutrition Examination Survey

Longitudinal study run by the CDC that has shown a decline in testosterone levels over time.

CDC

Organization that runs the NHANES study, which has tracked testosterone levels over decades, showing a decline.

Studies & Research

Carlsen et al.

A landmark paper from the early 90s by a group in Denmark that showed a temporal decline in semen quality over 50 years; a controversial study.