Smaller Penis Size and Phthalates

Spam email is replete with advertisements for ways to increase penis size and to enhance masculinity and virility. A sobering study suggests that exposure to phthalates before birth may under-virilize boys, which can be seen with a shorter penis length, thinner penis width, smaller and less distinct scrotum, shorter distance between the anus and scrotum, and higher likelihood of undescended testicles.

The study was conducted by researchers from several medical schools and the National Center for Environmental Health, and appeared online May 27, 2005 in the NIH journal Environmental Health Perspectives. This may prove to be a study of monumental importance.

Phthalates are a group of chemicals that make plastics more pliable. New in the environment over the last 50 years or so, they are now widely used in many plastic products, including wraps, bags, medical equipment, and toys. They are also used in many personal care products, from makeup to shampoos to soaps, and in paints and pesticides. They’re extremely common. It’s well understood that high levels of phthalates make male animals more feminine, with altered genitals, altered behavior, poor quality sperm, and increased infertility. But the effect on human babies has not been well studied. Can they bend the genders of baby boys?

In this study, one set of researchers collected and analyzed the urine from pregnant women for nine different phthalates. All of their urine contained phthalates, but the amounts varied widely. Later, different researchers collected detailed measurements of the 134 boys’ genitals. Matching the measurements to the urine samples produced dramatic results. Babies whose moms were in the top quartile of 4 of the different phthalates in their urine ranged from 3 to more than 10 times more likely to have an anogenital index (AGI) shorter than expected, when compared to babies whose moms were among the 25 percent with the lowest levels of these phthalates. No differences were detected with the other 5 types of phthalates.

This study is like a signal flare. It lights the sky with news that substances from the plastics, paints, pesticides, and personal care products we use get into our bodies, where they can change the babies that pregnant women are carrying. But it also highlights how little we know about these substances and their effects on human health. Clearly, some of the many types of phthalates are more dangerous than others – but we don’t really know much about which are which. Or about how these and other chemicals interact with each other in our bodies. But this study is also exciting because it suggests we might find ways to be rescued from our current situation of increasing infertility, genital, and gender problems.

Published on: December 01, 2005
About the Author
Photo of Alan Greene MD
Dr. Greene is a practicing physician, author, national and international TEDx speaker, and global health advocate. He is a graduate of Princeton University and University of California San Francisco.
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