The Fertility Test Most Men Are Never Offered | Dr Michael Eisenberg and Dr Natalie Crawford

What It Covers

Dr Michael Eisenberg, Stanford urologist and male fertility specialist, joins reproductive endocrinologist Dr Natalie Crawford to examine why male fertility testing is systematically neglected. They cover semen analysis parameters, how sperm health predicts long-term disease risk, the damage caused by unsupervised testosterone use, declining global sperm counts, paternal age effects, and concrete steps men can take to optimize reproductive and overall health.

Key Questions Answered

• •Semen analysis as a health biomarker: Sperm health functions as a "check engine light" for overall male health, predicting future chronic disease risk beyond fertility. A Danish study tracking men for up to 50 years found every semen parameter — volume, concentration, motility, morphology — correlated with age of death. Men with low sperm counts show higher rates of psoriasis, rheumatoid arthritis, and metabolic syndrome, even years before diagnosis. A semen analysis provides health intelligence that BMI and smoking status alone cannot.
• •The 1-in-3 male causation gap: Male factors solely explain roughly one-third of infertility cases, contribute to another third alongside female factors, yet current guidelines only recommend semen analysis after a couple fails to conceive for a full year. Surveys of infertile couples show males go unevaluated 25–33% of the time. Couples have undergone up to a year of IUI without a single semen analysis performed, wasting time, money, and emotional resources when a zero-sperm condition was present from the start.
• •Six semen parameters to request: A complete semen analysis covers volume, concentration, motility, morphology, pH, and DNA sperm fragmentation. Most standard clinic and at-home tests omit DNA fragmentation, which measures oxidative damage to sperm DNA and is now recommended by ASRM after two or more pregnancy losses. Total motile sperm count — calculated as volume × concentration × motility percentage — is the most clinically useful summary figure, with 40 million total motile sperm considered the threshold for optimal natural conception odds.
• •Testosterone replacement destroys sperm production: Exogenous testosterone acts as a contraceptive by suppressing FSH and LH signals from the brain, halting spermatogenesis and causing testicular atrophy. Intratesticular testosterone levels need to be roughly 10 times higher than blood levels to support sperm production — injectable TRT cannot replicate this. Recovery after stopping TRT takes 6–12 months and is not guaranteed, particularly after prolonged use. Men at unregulated testosterone clinics routinely receive no semen analysis, no fertility counseling, and no investigation into why testosterone is low.
• •Cannabis negatively impacts sperm and pregnancy outcomes: Daily cannabis use is associated with reduced sperm concentration, motility, and lower embryo development rates in IVF cycles. Women whose partners use cannabis — even if they do not use it themselves — show higher miscarriage rates. In IVF settings, switching from nightly cannabis use to abstinence, then waiting three months for a full spermatogenesis cycle, has produced measurably different outcomes. Edible THC concentrations can exceed smoked forms, making all delivery methods relevant for pregnancy outcome data.
• •Paternal age effects begin at 40, accelerate past 50: The American Society of Reproductive Medicine defines advanced paternal age as over 40. Past age 50, statistically significant increases emerge in autism spectrum disorder, schizophrenia, autosomal dominant conditions like dwarfism, and genomic imprinting disorders. Sperm freezing before age 40 is a low-cost, low-burden intervention — at-home collection kits allow mail-in banking without clinic visits. Each spermatogenesis cycle takes approximately 90 days, meaning sperm quality reflects the preceding three months of lifestyle, health, and exposures.
• •Lifestyle changes improve sperm within 90 days: Unlike eggs, which accumulate damage over decades, sperm regenerate on a roughly three-month cycle, making male fertility one of the most modifiable reproductive variables. Chronic inflammation and insulin resistance are the strongest shared drivers of poor sperm and egg quality. Reducing obesity, eliminating daily cannabis, avoiding heat exposure to the testes, limiting endocrine-disrupting chemical exposure, and addressing conditions like varicocele — present in 40% of infertile men — can produce measurable semen parameter improvements within a single spermatogenesis cycle.