Decline in Testosterone For General Population

[Phil Goodman]

We’ve all heard about declines in testosterone levels among men over the past few decades… with around 1% drop per year being often quoted(and supported by at least some studies). So I wondered what that would look like if you extrapolate it back to the 50’s. Studies below which show the drop over the past few decades, then my interaction with Claude with regard to what we may be able to tell with regard to what that means for trying to determine what it would look like 75 years ago. Obviously the studies are more validated by science, but I do think the thought experiment with Claude is directionally accurate, even if we can never know for sure how today’s society compares to the past with regard to hormones.

A population-level decline in serum testosterone levels in American men - PubMed

These results indicate that recent years have seen a substantial, and as yet unrecognized, age-independent population-level decrease in T in American men, potentially attributable to birth cohort differences or to health or environmental effects not captured in observed data.

pubmed.ncbi.nlm.nih.gov

Secular trends in testosterone- findings from a large state-mandate care provider - PMC

Several studies from the US and Europe have shown a population-level decline in serum testosterone in men from 1970’s to early 2000’s. However, to the best of our knowledge, no study examining population-level decline in testosterone has been ...

pmc.ncbi.nlm.nih.gov

Prompt:

Now extrapolate out what the levels would’ve been in 1950 based on those trends. Next, determine what that means for trt goals. For example if we want to keep men in the top 25% of the range for maximum benefits, what would that range have looked like in 1950?



PART 1: What Were Testosterone Levels in 1950, and What Does That Mean for TRT?
This is an extrapolation beyond the available data, so treat these numbers as directional estimates rather than hard facts — but the math is illuminating.
Establishing the Trend
The best documented data points for population-level testosterone decline come from a landmark Boston-area study:
• 1987–89: 501 ng/dL (median)
• 1995–97: 435 ng/dL
• 2002–04: 391 ng/dL
That’s a drop of roughly 110 ng/dL over 15 years, or about 7.3 ng/dL per year — approximately 1.2–1.5% annually. Crucially, this decline was shown to be age-independent, meaning it’s a generational shift, not just men getting older.
Extrapolating Back to 1950
From 1987 back to 1950 = 37 years.
At ~7.3 ng/dL/year:
501 + (37 × 7.3) ≈ ~770 ng/dL
At 1.2%/year compounding:
501 × (1.012)^37 ≈ ~780 ng/dL
Both methods converge around 750–800 ng/dL as the estimated median testosterone for a man in 1950.
Reconstructing the 1950 Distribution
Using modern reference data, the current male testosterone distribution looks roughly like this:
• 25th percentile: ~350 ng/dL
• 50th percentile (median): ~450 ng/dL
• 75th percentile: ~625 ng/dL
• 90th percentile: ~800 ng/dL
The distribution has shifted downward by approximately 300–330 ng/dL from 1950 to today. Applying that shift back:
• 25th percentile — Modern: ~350 | Est. 1950: ~680
• 50th percentile — Modern: ~450 | Est. 1950: ~775
• 75th percentile — Modern: ~625 | Est. 1950: ~950
• 90th percentile — Modern: ~800 | Est. 1950: ~1,130
What This Means for TRT
This is where it gets striking. The top 25% threshold in 1950 was roughly 950 ng/dL — a number that today sits near the top 5–10% of the modern population, and at or above the upper limit of most lab “normal” ranges (typically capped at 900–1,000 ng/dL).
If the goal of TRT is to restore men to what was historically a normal, healthy hormonal environment — rather than just avoiding being “low” by today’s degraded standards — then targeting 900–1,000+ ng/dL has a legitimate historical basis.
The uncomfortable takeaway: most TRT protocols targeting the “mid-normal modern range” of 500–600 ng/dL are likely restoring men to roughly the bottom half of what a healthy 1950s male population looked like. We’ve been calibrating “optimal” against a broken baseline.

 

[Phil Goodman]

And obviously in many ways people lived much healthier lifestyles back then. That is true in many ways. However, post WWII also saw an explosion in some of the worst culprits with regard to environmental toxins. So while diet and lifestyle were generally better overall, there are still plenty of things that could’ve really kicked off or escalated the decline in endocrine system optimization. So I followed up with this prompt:


What environmental factors back then would’ve been most likely to contribute to declines in levels? For example, the lead, asbestos, herbicides, pesticides, and many other things were very harmful. How much of an impact do those have on hormones and what other factors would’ve been at play?



PART 2: What Environmental Factors Caused the Decline — and Was 1950 Actually a Clean Baseline?
This is where the analysis gets more nuanced, because it reveals an important paradox.
The Core Paradox
Many of the most potent hormone-disrupting chemicals were at peak exposure levels in the 1940s–70s, not today. Lead, DDT, PCBs, and industrial heavy metals were largely unregulated and saturating the environment during that period. This means our 750–800 ng/dL estimate for 1950 may actually be deflated — those men were being hormonally suppressed too, just by different chemicals than we are today. A truly pre-industrial baseline may have been significantly higher.
Lead (peaked ~1960s–70s)
Lead accumulates in the body and attacks the hormonal system at multiple levels — it damages the testes directly, and with long-term exposure it also disrupts the hypothalamic-pituitary axis, blunting the LH and FSH signals that tell the testes to produce testosterone in the first place. Leaded gasoline wasn’t phased out in the US until the 1980s, meaning blood lead levels in men from the 1950s through 1970s were dramatically higher than they are today.
DDT and Organochlorine Pesticides (peak use 1940s–1970s)
DDT is an estrogen mimic — it binds to estrogen receptors and triggers estrogenic responses in the body. Its primary metabolite, DDE, has anti-androgenic properties, meaning it blocks androgen receptors and interferes with testosterone’s ability to act on target tissues. In populations with high DDT/DDE blood concentrations, studies have found reduced testosterone, lower LH and FSH, and elevated estradiol and SHBG. Higher SHBG is particularly problematic because it binds free testosterone, making even a “normal” total testosterone reading largely unavailable to tissues.
DDT also crosses the placental barrier, meaning men born during the peak DDT era had in-utero exposure that could affect their hormonal potential from birth.
PCBs
Polychlorinated biphenyls followed similar mechanisms to DDT — estrogenic, anti-androgenic, and persistent in fat tissue. They were used extensively in electrical equipment, industrial fluids, and building materials through the 1970s and bioaccumulated up the food chain.
Atrazine (1950s–present)
Atrazine is a widely used herbicide that works by upregulating aromatase — the enzyme that converts testosterone into estrogen. Research has shown it chemically castrates male frogs at EPA-approved concentrations. It is still legal in the US today (banned in the EU) and remains one of the most detected pesticides in American groundwater.
What 1950s Men Had Going FOR Them
Despite the toxic burden, mid-century men had significant hormonal advantages that likely more than compensated:
• Obesity rates of roughly 10% vs. ~40% today. Body fat, especially abdominal fat, is loaded with aromatase enzyme — the same enzyme atrazine upregulates. The more fat tissue, the more testosterone gets converted to estrogen.
• Far higher levels of physical labor and daily movement. Exercise directly stimulates Leydig cell activity and testosterone production.
• No plastics, BPA, or phthalates. These chemicals didn’t exist at population scale until the 1950s–60s and are now essentially inescapable. They are potent androgen receptor blockers.
• No ultra-processed food at scale. The modern diet — seed oils, high fructose corn syrup, ultra-processed packaged food — correlates strongly with hormonal disruption and is a post-WWII phenomenon.
• Better sleep architecture. Without screens and artificial light disrupting circadian rhythms, deep sleep was likely more robust. The majority of daily testosterone production occurs during sleep.
• Lower chronic cortisol. Cortisol and testosterone have a direct inverse relationship — cortisol suppresses testosterone production, and the chronic low-grade stress of modern life is a relatively new phenomenon.
Comparing the Two Eras
• Lead exposure: Much worse in 1950s–70s → suppressed T then
• DDT/organochlorines: Much worse in 1950s–70s → suppressed T then
• Plastics/BPA/phthalates: Far worse today → suppresses T today
• Obesity: Far worse today → suppresses T today
• Physical activity: Far better in 1950 → raised T then
• Sleep quality: Likely better in 1950 → raised T then
• Ultra-processed food: Far worse today → suppresses T today
• Atrazine: Present in both eras → suppresses T in both
The Bottom Line
Neither era was hormonally “clean.” But the lifestyle advantages of 1950 (leanness, physical labor, sleep, whole food diet) likely outweighed the chemical disadvantages enough to maintain meaningfully higher testosterone. A truly pre-industrial man — pre-1880s, before synthetic chemicals, with high physical demand and no processed food — may have had a median testosterone that’s nearly unimaginable by today’s standards, potentially north of 900–1,000 ng/dL as a population average.
This strengthens the argument that modern TRT “normal ranges” are not benchmarks of healthy human biology. They are benchmarks of a chemically and metabolically compromised modern population. Restoring men to the top quartile of 1950s levels — roughly 950+ ng/dL — is not supraphysiologic. It may be closer to what human male physiology was actually designed to operate at.