(RxWiki News) About 2 to 5 percent of newborn boys have undescended testicles at birth. Usually, the testicles descend on their own by the time the child is 6 months old.
But, if the condition persists, the boy may be at higher risk for lower fertility or testicular cancer when he gets older.
A new study, not yet published in a journal, found that a chemical found in plastics may be related to undescended testes.
The chemical is called Bisphenol A, or BPA. It's unclear whether this chemical might contribute to undescended testicles or be related to it in some way.
"Look for BPA-free products."
The study, led by Patrick Fenichel, MD, PhD, of the Centre Hospitalier Universitaire de Nice, looked at the possible relationship between the chemical Bisphenol A (BPA) and undescended testes in infant boys.
BPA is a chemical used in manufacturing a wide range of hard plastics and can be used in the linings of food cans or in dental sealants. It is known to be an endocrine disruptor, which means it can interfere with the endocrine system, the body system that creates and regulates hormones.
The researchers compared a number of different blood test results among 180 boys in Nice, France between 2002 and 2005.
In this group were 52 boys who were born after at least 34 weeks of pregnancy (38-40 weeks is full-term) and had one or two undescended testicles.
Half of these boys' testes eventually descended by the time they were 3 months old while the other 26 boys' testes remained undescended.
The other 128 boys, whose testes were descended at birth, were used in the study as a comparison group.
They were matched to the boys with undescended testes in terms of weight, time of birth and the number of weeks their mothers were pregnant upon giving birth.
The lab work for all the boys included testing the amount of BPA and testosterone found in their umbilical cord blood and the amount found of a specific protein hormone produced in the sex organs.
The researchers also measured the amount of certain chemicals that were found in the boys' mothers' breastmilk. These are chemicals also found in manufactured products, including plastics, that are known to be endocrine disruptors as well.
The researchers found that the protein hormone they tested for, called INSL3, was decreased in the boys with undescended testes, especially those who later had their testes descend.
There was no difference in testosterone levels between the boys who had descended or undescended testes.
The researchers did not find higher levels of any of the endocrine disruptor chemicals in the group of boys with undescended testes.
However, when the researchers looked at the results for the full group of 180 boys, they found a relationship between the amount of BPA in the boys' blood and their levels of the protein hormone INSL3.
The more BPA the boys had in their blood, the lower their INSL3 levels were.
The authors wrote that INSL3 plays a major part in whether boys' testicles descend.
They found a lower amount of INSL3 in the newborns with undescended testes, and they found that INSL3 is decreased when BPA levels are increased.
"This is the first time that a direct link between fetal [unborn baby] exposure to environmental endocrine disruptors, decreased INSL3 and [undescended testis] has been established in humans," the researchers wrote.
An unborn baby's "...exposure to a cocktail of environmental endocrine disruptors with estrogenic and antiandrogenic effects [the ability to affect male and female sex hormone] should be considered as one of the cofactors, associated with genetic susceptibility, contributing to this frequent, complex and multifactorial disease," they wrote.
The study does not mean that BPA causes undescended testicles. There is a link between hormones and BPA that needs further research.
The research was presented June 16 at The Endocrine Society's 95th Annual Meeting in San Francisco. It has not been reviewed by other researchers for publication in a journal yet.
The research was funded by the PHRC Clinical Research Program of the French Ministery of Health. The authors reported no conflicts of interest.