Penises Are Growing Bigger Fast: Study

A new study out of Stanford has found that while, over the last 30 years, cisgender men's sperm counts and testosterone levels have decreased, their penises have gotten longer.

Michael Eisenberg, a medical doctor and professor of urology at Stanford Medical School, is concerned about declining sperm quality and testosterone level trends in male reproductive health data. The finding made him explore whether any other differences in men's reproductive health are cause for alarm, according to Stanford's Scope blog.

Researchers compiled data from 75 studies reporting penile lengths for 55,761 men between 1942 and 2021 for a study published on February 14 in The World Journal of Men's Health.

They observed a 24 percent increase in the average erect penis length over 29 years.

Eisenberg said that many studies have looked at men's reproductive health from the aspect of sperm count and testosterone levels, which have decreased for men over time. He noted that higher congenital sex-organ abnormalities have also contributed to data about men's health.

"Another measurement we've seen reported in some men's health research is penile length, and no one has taken a systematic look at that," he said on the blog. "Given the trends we'd seen in other measures of men's reproductive health, we thought there could be a decline in penile length due to the same environmental exposures."

He explained that the team conducted a "meta-analysis" examining reports on flaccid, stretched, and erect penis length to create a comprehensive database.

"What we found was quite different from trends in other areas of male fertility and health. Erect penile length is getting longer, from an average of 4.8 inches to 6 inches, over the past 29 years," Eisenberg said.

Because human reproduction is essential to preserving humankind, Eisenberg says, an overall rapid change in development is concerning.

"If we're seeing this fast of a change, it means that something powerful is happening to our bodies. We should try to confirm these findings, and if confirmed, we must determine the cause of these changes," he said.

Several factors could contribute to the changes, including exposure to pesticides and chemicals in personal hygiene products interacting with the body's natural hormones.

According to him, many chemicals interrupt hormone levels in the environment and food. In addition, Eisenberg says that some of these increased exposures to chemicals have been linked to boys and girls going through puberty at younger ages, which could affect genital development.

Eisenberg says that as a way to monitor for changes, doctors ought to add measuring penis size to a battery of regular measurements that providers already monitor.

"Just as we measure height and weight every year across the U.S., this is something else we could measure in a systematic fashion because it may turn out to be an early indicator of changes in human development," he said.