BPA Exposure Tied to Undescended Testicles in Boys
Early study doesn't prove that common chemical causes the condition, experts say
This appears to be the first study that shows a link between INSL3 levels and BPA, said Shanna Swan, a professor and vice chair for research and mentoring in the department of preventive medicine at the Icahn School of Medicine at Mount Sinai, in New York City.
"This hormone INSL3 has not been, to my knowledge, previously linked to any endocrine-disrupting chemicals," Swan said. "It's interesting, definitely, and it's an important step."
For the study, Fenichel and his colleagues studied 180 newborn boys between 2003 and 2005, including 52 boys born with one or two undescended testicles. They tested the infants' umbilical cord blood to measure levels of BPA and INSL3.
The infants with cryptorchidism had significantly lower levels of INSL3 compared to newborns without the birth defect, the authors reported. Fenichel speculated that BPA, considered a hormone disruptor, might repress expression of the gene that promotes production of INSL3.
The U.S. Food and Drug Administration has banned the use of BPA in products such as baby bottles and sippy cups, but the chemical continues to be used in many other consumer products.
The most prominent continuing use of BPA is in the lining of aluminum and tin cans, where it prevents corrosion. "The linings of tin cans is probably the biggest source of our exposure," Swan said. "There is almost no canned food that comes in BPA-free cans."
BPA also is found in cash register receipts. "To have a cash register receipt that doesn't require ink, it is coated in BPA," Swan said, noting that studies have found increased BPA levels in the urine of people who have touched a receipt.
Both Swan and Dr. Leonardo Trasande, an associate professor of pediatrics, environmental medicine and health policy at NYU Langone Medical Center in New York City, noted that there are limitations to the new study.
BPA typically is not measured in blood, Trasande and Swan said. In most cases, doctors use urine to measure BPA exposure.
Swan also said the study does not make a clear link between BPA and undescended testicles, since BPA levels appeared consistent in all the newborns regardless of whether they had the birth defect.