Two new studies have raised further questions marks over the health effects of bisphenol A (BPA), according to the Endocrine Society in the United States.
The international research body said studies to be presented at its annual meeting next week will document concerns linking exposure to BPA to possible harmful effect of the development of male testicular function and that women with the polycystic ovary syndrome (PCOS) may be more vulnerable to exposure to the chemical.
In their study of male rats, Benson Akingbemi et al said their findings showed harmful effects of BPA at the cellular level, specifically in Leydig cells. These cells in the testis secrete testosterone, the main sex hormone that supports male fertility. After birth, Leydig cells gradually acquire the capacity for testosterone secretion.
The researchers found that process of testosterone secretion fell in male offspring of female rats that received BPA during pregnancy and while nursing. The mothers were fed BPA in olive oil at a dose of either 2.5 or 25 micrograms of BPA per kilogram of body weight – less than the 50 micrograms per kilogram of body weight FDA daily upper limit of safe exposure.
A control group of pregnant rats received olive oil without BPA. Male offspring, after weaning at 21 days of age, received no further exposure to the substance.
The scientists studied the development of Leydig cells in male offspring and the capacity for testosterone secretion was assessed at 21, 35 and 90 days of age. The amount of testosterone secreted per Leydig cell was found to be much lower in male offspring after early-life exposure to BPA than in offspring from control unexposed animals, they said
"We are seeing changes in the testis function of rats after exposure to BPA levels that are lower than what the Food and Drug Administration and Environmental Protection Agency consider safe exposure levels for humans," said Akingbemi. "This is concerning because large segments of the population, including pregnant and nursing mothers, are exposed to this chemical."
Polycystic ovary syndrome
This study found that BPA is elevated and associated with higher levels of male hormones in the blood of women with PCOS compared with healthy women. These findings held true for both lean and obese women with PCOS, said Evanthia Diamanti-Kandarakis, study co-author and professor at the University of Athens Medical School in Greece.
"Women with the polycystic ovary syndrome should be alert regarding this environmental contaminant's potential adverse effects on reproductive aspects of their health problem," she said.
The researchers divided 71 women with PCOS and 100 healthy female control subjects into subgroups matched by age and body composition (obese or lean). Blood levels of BPA, compared with those of controls, were nearly 60 percent higher in lean women with PCOS and more than 30 percent higher in obese women with the syndrome.
They also discovered that as the BPA blood level increased, so did the concentrations of the male sex hormone testosterone and androstenedione, a steroid hormone that converts to testosterone.
Diamanti-Kandarakis said women with PCOS may want to limit their exposure to BPA but stressed that no research had yet proved that reducing BPA in PCOS would have beneficial effects.