Dr Shanna Swan11 April 2024

Why Are Men’s Testosterone Levels Plummeting? - Dr Shanna Swan - #769

0Frameworks

15Insights

Insights & moments

The myth-busts, hot takes, explainers, and tools worth keeping.

Myth Buster· 1

Myth Buster08:30

Phthalates Lower Sexual Satisfaction in Women

Contrary to assumptions that only men are affected by hormone disruptors, phthalates reduce testosterone in both sexes. In women, higher phthalate exposure correlates with lower sexual satisfaction and reduced frequency of sex.

Phthalates lower testosterone in both men and women.
Women with higher phthalate levels report less sexual satisfaction.
They also have sex less frequently, indicating a direct impact on libido.
This shows endocrine disruption affects couples' intimacy and fertility.

“When the woman had low phthalates, she was less satisfied and she had sex less often.”
Dr. Shanna Swan · 09:10

#phthalates#libido#testosterone#sexual health

Hot Take· 1

Hot Take13:00

Low Libido May Be Driving Fertility Collapse

Declining libido — potentially due to endocrine disruption — may be a fundamental driver of falling birth rates. Reduced sexual desire leads to fewer relationships, less marriage, and fewer babies, independent of social or economic factors.

Lower libido reduces motivation to seek partners or have sex.
This impacts fertility more directly than cognitive or economic reasoning.
Both men and women are affected by hormone-disrupting chemicals.
Declining sexual activity is a proximate cause of population decline.

“If you just look way closer to home, sex is just less of a driver potentially due to reduced libido.”
Dr. Shanna Swan · 14:10

#libido#fertility#endocrine disruption#birth rates

Explainer· 8

Explainer00:00

Why Testosterone May Be Declining in Men

While definitive global trends in testosterone levels are still under study, multiple signals suggest a decline. Clinical data show rising testosterone use among young men, possibly due to falling natural levels or social pressures around masculinity and body image.

Research on long-term testosterone trends is ongoing and not yet conclusive.
Use of testosterone therapy, especially by younger men, is increasing alarmingly.
It's unclear whether low libido, body image issues, or endocrine disruption drive the trend.
Sperm count data is more robust than testosterone data due to longer study history.

“There are a lot of signals suggesting that testosterone is in trouble.”
Dr. Shanna Swan · 00:50

#testosterone#men's health#endocrine disruption#hormones

Explainer02:00

Why We Know More About Sperm Count Than Testosterone

Sperm count has been studied for over 65 years and is routinely measured for fertility assessments, vasectomies, and medical exams. In contrast, testosterone levels are less frequently tested, leading to sparser long-term data despite greater public awareness today.

Sperm count has a long history of clinical measurement across diverse reasons.
Testosterone testing is less common and not routinely tracked over time.
More men today know their testosterone levels than sperm counts, but historical data is limited.
Routine sperm testing provides a richer dataset for trend analysis.

“Sperm count has been under study for 65 years... there's been very little on testosterone.”
Dr. Shanna Swan · 02:20

#sperm count#testosterone#fertility#data trends

Explainer04:00

How Testosterone Shapes Fetal Development

Testosterone plays a critical role in early fetal development, particularly in differentiating male genitalia. Without sufficient testosterone at the right time in the first trimester, genetic males may develop incompletely masculinized genitalia.

Testosterone production begins in the first trimester in genetic males.
It triggers the development of male-typical genitalia from a neutral starting point.
Low testosterone in utero can lead to smaller penis, undescended testicles, and other changes.
This early hormonal influence is irreversible and foundational.

“Testosterone is what kicks off the genetic male differentiating himself from the genetic female.”
Dr. Shanna Swan · 05:10

#testosterone#fetal development#endocrine disruption#prenatal health

Explainer06:00

Anogenital Distance: A Key Marker of Prenatal Hormone Exposure

Anogenital distance (AGD) — the space between the anus and genitals — is longer in males due to prenatal testosterone exposure. Shorter AGD in males indicates incomplete masculinization and is linked to endocrine disruptors like phthalates.

AGD is significantly longer in males due to testosterone exposure in utero.
Shorter AGD in males is a sign of incomplete masculinization.
It's a measurable biomarker of endocrine disruption during fetal development.
Until recently, AGD was only studied in animals, not humans.

“The anogenital distance... it was not considered interesting for humans and then I showed it was extremely interesting.”
Dr. Shanna Swan · 06:20

#AGD#endocrine disruption#prenatal development#phthalates

Explainer15:30

Low Sperm Count Linked to Shorter Lifespan

Men with low sperm count have higher rates of heart disease, diabetes, and reproductive cancers. Evidence now shows they also have a shorter overall lifespan, suggesting sperm count is a biomarker of general health.

Low sperm count correlates with impaired hormone systems.
It's linked to higher risks of heart disease, diabetes, and cancer.
Multiple studies confirm men with low sperm count die earlier.
Sperm health reflects lifelong hormonal and metabolic function.

“Men and women who have impaired hormone systems are more likely to have other medical problems... you die earlier.”
Dr. Shanna Swan · 16:10

#sperm count#longevity#men's health#hormones

Explainer19:30

Sperm Counts Are Falling Worldwide at 1% Per Year

A meta-analysis of global data shows sperm counts declining at over 1% per year since 1973, accelerating to 2% after 2000. This trend is now confirmed in all regions, including Asia, Africa, and South America.

Sperm counts are dropping at 1% per year globally.
The decline has accelerated to 2% annually since 2000.
Initial data was Western-heavy, but now includes diverse global populations.
The trend is consistent and worsening, not stabilizing.

“Sperm counts are going down at about 1% per year... and the rate of decline is increasing.”
Dr. Shanna Swan · 20:10

#sperm count#fertility#global health#endocrine disruption

Explainer55:30

Microplastics Are Re-Entering the Human Body

Micro- and nanoplastics from degraded plastic waste are now found in water, air, and human cells. These tiny particles can carry harmful chemicals and cause physical damage, similar to asbestos, representing a new frontier in endocrine disruption research.

Microplastics come from breakdown of recycled and discarded plastics.
They are found in drinking water, air, and human tissues.
They can carry toxic chemicals and cause physical harm like asbestos.
This is a rapidly emerging area of concern in environmental health.

“These chemicals that are put out there... they're here, they're back.”
Dr. Shanna Swan · 56:50

#microplastics#water safety#endocrine disruption#pollution

Explainer63:00

Endocrine Disruptors May Alter Child Brain Development

Prenatal exposure to phthalates can affect brain development, leading to delayed language skills in girls and less gender-typical play behavior in boys. These findings suggest hormone disruptors influence not just physical but cognitive and behavioral development.

Phthalate exposure in pregnancy is linked to delayed language in girls.
Boys exposed to phthalates show less male-typical play behavior.
The brain is sexually dimorphic and influenced by prenatal hormones.
These effects occur even when genital development appears normal.

“Exposure to these chemicals in pregnancy are going to affect the masculinization of the brain.”
Dr. Shanna Swan · 64:50

#phthalates#brain development#prenatal exposure#child development

Story· 3

Story22:00

Denmark's Sperm Counts May Be Stabilizing

Denmark, one of the best-studied countries due to long-term military recruit data, shows signs that sperm count decline may be leveling off. Finland, once better, is now catching up in decline rates.

Denmark has extensive data from military recruits tested over decades.
Recent data suggests sperm counts are no longer declining there.
Finland, previously healthier, is now seeing faster decline.
This contrast raises questions about environmental or policy differences.

“In Denmark, the rate of decline seems to have leveled up.”
Dr. Shanna Swan · 22:10

#sperm count#Denmark#Finland#public health

Story46:00

How Milking Machines Introduce Phthalates Into Milk

Milk from hand-milked organic farms has no phthalates, but milk from mechanized systems contains them. The plastic tubing in milking machines contains phthalates that leach into warm milk, adding another exposure route.

Phthalates are added to plastic tubing to make it soft and flexible.
They easily leach into warm liquids like milk during collection.
Hand-milked organic milk has no detectable phthalates.
This shows how food processing introduces endocrine disruptors.

“Milk that's collected through a milking machine... the phthalates in the tubing go into the milk, go into the bucket, go into the bottle, go…”
Dr. Shanna Swan · 46:40

#phthalates#dairy#food safety#endocrine disruption

Story72:00

Israel's Fertility Rates Defy Global Decline

While nearly every country sees falling fertility rates, Israel is an exception. This is due to universal access to assisted reproductive technologies, which are fully covered by the state, allowing couples to have children regardless of biological challenges.

Israel's fertility rate hasn't declined like the rest of the world.
The country guarantees access to IVF and other ARTs.
This policy buffers against biological fertility decline.
It highlights how social policy can counteract physiological trends.

“In Israel, people are guaranteed to have children by artificial reproductive technology — and their fertility is not declined.”
Dr. Shanna Swan · 72:40

#fertility#Israel#IVF#public policy

Tool· 1

Tool49:00

How to Reduce Exposure to Hormone-Disrupting Chemicals

To minimize exposure, avoid plastic food containers, especially when heating. Use glass or silicone instead. Choose unpackaged produce, avoid microwaving in plastic, and consider water filtration methods like reverse osmosis or distillation.

Never microwave food in plastic containers.
Glass containers (like Pyrex) are safer for storage and heating.
Silicone is preferable to conventional plastic.
Reverse osmosis and distillation reduce microplastics and chemicals in water.

“Do not microwave your food in plastic — this podcast should be called that.”
Chris · 47:20

#endocrine disruptors#plastics#water filtration#lifestyle

Takeaway· 1

Takeaway26:30

Lifestyle Changes That Boost Sperm Count

Men can improve sperm health through diet, exercise, and avoiding harmful substances. Mediterranean diet, not smoking, maintaining healthy weight, reducing stress, and avoiding binge drinking all positively impact fertility.

Mediterranean diet improves sperm count compared to Western diet.
Smoking is a major risk factor for low sperm count.
Obesity and lack of exercise reduce fertility.
Stress and binge drinking also negatively affect sperm production.

#sperm count#lifestyle#diet#fertility