The T Files | Testosterone Science
by Keen Meds

The testosterone transdermal spray delivers bioequivalent pharmacokinetics to Androgel with faster drying, lower transfer risk, and no injection required.

Both injection microdosing and transdermal testosterone deliver small frequent doses — but they differ in adherence, polycythemia risk, and long-term outcomes.

Microdosing testosterone means smaller, more frequent doses that mimic the body's natural rhythm. Here's what the clinical evidence actually says.

Supraphysiological testosterone levels aren’t just unnecessary for TRT — the clinical data shows they are actively harmful. Here’s what happens above the normal range.

Supraphysiological testosterone levels aren't just unnecessary for TRT — the clinical data shows they are actively harmful. Here's what happens above the normal range.

Most men on weekly testosterone injections feel great for a few days, then terrible by day 6. The science explains exactly why — and what to do about it.

Transdermal testosterone bypasses first-pass liver metabolism and delivers continuous absorption that mimics natural testicular production — the most…

Testosterone gels leave active hormone on the skin surface for hours after application — enough to transfer to children and partners through casual…

A metered-dose transdermal spray delivers the same systemic testosterone exposure as AndroGel — with faster drying, less surface residue, and…

The Hypospray delivery system from TDSC uses proprietary formulation chemistry to improve transdermal testosterone absorption — validated as…

A well-designed transdermal spray addresses every major failure mode in testosterone delivery history — first-pass loss, pharmacokinetic cycling, skin…

TRT is more prescribed, better evidenced, and more accessible than ever — but significant diagnostic gaps and prescribing without adequate evaluation…

TRT monitoring requires specific labs at specific intervals — hematocrit, PSA, estradiol, and testosterone levels that together confirm the therapy is…

When low testosterone is caused by obesity, sleep apnea, or opioids rather than HPT axis failure, the treatment question becomes: fix the cause, start…

Good testosterone therapy follows a structured protocol: two morning baseline measurements, defined monitoring intervals, and symptom reassessment…

The arc from Berthold's 1849 rooster experiment to the metered-dose testosterone spray of 2025 passes through a Nobel Prize, a monkey gland scandal,…

Women produce testosterone throughout their lives — and it declines significantly with age and surgery, with consequences medicine has been slow to…

Hypoactive sexual desire disorder, fatigue, and reduced wellbeing in women are documented consequences of testosterone deficiency — with 36 trials…

After 36 randomized controlled trials in 8,000+ women, the FDA rejected the only testosterone product designed for women — citing long-term safety…

Women require 10–15 times less testosterone than men — a dosing range where precision matters enormously and supraphysiologic exposure causes virilization.

A 42-year gap separates the first men's testosterone muscle study from the first comparable women's dose-response trial — a disparity that defines the…

Men produce 1,000 sperm per second. Suppressing that factory to contraceptive levels while maintaining testosterone's other functions is a genuine…

The WHO's landmark trials proved male hormonal contraception works — and that weekly injections of supraphysiologic testosterone are not a practical…

Dimethandrolone undecanoate is an oral male contraceptive candidate that completed Phase II with 89% hormonal suppression — and has been waiting for…

A Phase IIb trial of nestorone plus testosterone gel achieved 86% sperm suppression in men — then COVID disrupted enrollment before full efficacy data…

The science of male hormonal contraception is settled. What is missing is the pharmaceutical investment, regulatory pathway, and cultural will to turn…

The TOM trial stopped early after 5 months — 23 cardiovascular events in the testosterone group versus 5 in placebo — launching a decade of…

A 2013 JAMA meta-analysis claimed testosterone increased adverse cardiovascular events by 29% — but included data from female patients in a male…

While debate focused on whether testosterone caused cardiac events, the existing evidence consistently showed low testosterone was itself a…

The TRAVERSE trial enrolled 5,246 men in the largest testosterone safety study ever conducted — and found no increased risk of heart attack or stroke.

TRAVERSE resolved the major cardiovascular question but identified secondary risks — atrial fibrillation, pulmonary embolism — that now require…

The European Male Aging Study found obese men had 8.7 times the risk of secondary hypogonadism compared to normal-weight men — establishing the…

Adipose tissue converts testosterone to estradiol through aromatase — the more visceral fat present, the more testosterone is lost to this one-way…

Insulin resistance suppresses SHBG, which can make free testosterone appear normal even when total testosterone is significantly deficient — a…

Low testosterone causes fat gain and fat gain causes low testosterone — a self-reinforcing cycle that can be entered from either direction.

Testosterone therapy in hypogonadal men reduces fat mass and improves metabolic markers — but the effect size is modest and TRT is not a weight-loss drug.

The first injectable testosterone required injections every 2–3 days due to its 20-hour half-life — a burden that defined early TRT.

Testosterone enanthate dominated TRT for half a century — effective, cheap, and deeply flawed in its pharmacokinetics.

Injection testosterone causes supratherapeutic peaks and subtherapeutic troughs — a pharmacokinetic rollercoaster the 1990 WHO consensus formally…

Long-acting testosterone undecanoate (Aveed) required an FDA REMS program after reports of pulmonary oil microembolism within minutes of injection.

Injection site pain, emotional cycling, and the gap between expectation and experience drive high early discontinuation in men starting injectable…

The first transdermal testosterone patch worked by exploiting scrotal skin's uniquely high permeability — five times better than anywhere else on the body.

Androderm solved the scrotal application problem but introduced application site reactions in nearly half of users — a tolerability crisis that gels…

Launched in 2000, AndroGel transformed TRT by delivering physiological testosterone without patches, injections, or significant skin reactions.

Testosterone gel residue on skin transfers to women and children through casual contact — causing virilization serious enough to earn the FDA's…

Injections peak too high and crash too low. Patches work but irritate half of users. Gels come closest to the 1990 WHO goal — but daily application…

In 1849, one physician and four roosters accidentally discovered how testosterone governs the male body.

In 1889, Brown-Séquard injected himself with dog testicular extract at age 72 and announced remarkable rejuvenation to the world.

For 3,000 years, castration documented what testosterone does to the male body — the longest unintentional clinical trial in history.

In the 1920s, Serge Voronoff transplanted chimpanzee testicular tissue into over a thousand men. It did not work.

In 1935, three independent laboratories isolated and synthesized testosterone in the same year, giving medicine its first real hormone.

The 1939 Nobel Prize in Chemistry went to testosterone research — announced the same month Germany invaded Poland.

Adolf Butenandt collected urine from Berlin policemen to isolate androsterone — yielding just 15 mg from 15,000 liters.

Leopold Ruzicka was a perfume chemist at Ciba Basel when he synthesized testosterone from cholesterol — independently of Butenandt.

Three breakthroughs in one year gave medicine a synthesizable molecule — and within two years, testosterone was in clinical use.

After 1939, the testosterone field exploded — new syndromes, new steroids, and a 1990 expert consensus that the standard of care still wasn't good enough.