Low T

Testosterone In Men Is More Stable Then We Thought — But 10 Factors Can Lower It

A new study upends established thinking about testosterone.

A man carrying a child on his shoulders in a tropical setting.
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We all know testosterone declines with age, but there are so many more factors that can make your testosterone levels drop, according to a new study of 25,000 men across the world. For some men, a dip in testosterone may not cause negative consequences, but for others it can lead to low testosterone, which can cause erectile dysfunction, reduced muscle mass, increased body fat, mood changes, and fatigue.

The study, conducted by an international team of researchers, found that the age-related testosterone decline really picks up once you hit 70 years old; around then, the testes start having trouble producing the sex hormone. Up until that age, however, testosterone levels remained fairly stable, according to the new research.

These findings conflict with previous research which found that testosterone levels decreased across the adult lifespan, which prompted a small group of scientists to suggest there should be age-specific cutoffs for low testosterone for men as young as those in their 20s, 30s, and 40s. Currently there is one cutoff for low testosterone regardless of age. And based on their findings, the authors of the new study suggest there should be a different cutoff for men 70 and over, but not for men of younger ages.

This is not to say your average man under 70 has more testosterone than we thought. Low T is still common enough — but is influenced by a number of external factors that we all have a little control over.

The biggest influence on testosterone levels was BMI, the new study found. As BMI increased, testosterone levels decreased, period. Diabetes and cancer were also both strongly correlated with lower levels.

Other health factors that seemed to correlate with lower testosterone levels were hypertension, heart disease, being a former smoker, using lipid-lowering or psychotropic drugs, and getting 75 minutes or less of vigorous physical activity per week. Fortunately, these are all health signs that your primary care provider should be tracking, and that you can often keep in check through exercise and diet and potentially medication.

"Men should be encouraged to engage in healthy lifestyle behaviors, as this should help maintain their body's own testosterone production," study author Bu Yeap, Ph.D., an endocrinologist and professor at the Medical School of the University of Western Australia in Perth, told MedPage Today.

Outside of health factors, a man’s relationship status loomed large in testosterone levels. Married men had lower testosterone levels. "A possible explanation could be that married men with families might be more stressed, and therefore have lower testosterone levels," Yeap said, "but our study wasn't designed to look further into this result."

Becoming a dad also decreases a man’s testosterone levels, potentially due to biological reactions from interacting with a pregnant partner. But that’s not a bad thing: A decrease in testosterone in dads is linked to greater involvement in the family and a lower risk of divorce. Importantly, this drop in testosterone doesn’t necessarily cause clinically low testosterone. Additionally, wives report higher relationship satisfaction when their husbands’ testosterone drops, and men with lower testosterone may make more friendships too.

"The main message is that a range of sociodemographic, lifestyle, and medical factors influence testosterone levels in men," Yeap said. "These need to be considered when clinicians interpret testosterone results from individual men, as testosterone levels might be lower than expected in the presence of these conditions, rather than being always due to a problem with the testes."