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Meer nadelen van Bisphenol-A*
Uit twee studies blijken de nadelen van Bisphenol-A (BPA) weer eens. De ene studie, weliswaar met ratten blijkt dat zwangere en zogende dieren die met hun voeding een dosis BPA kregen, lager dan een vergelijkbare toegestane waarde voor mensen, hadden mannelijke nakomelingen die later in hun leven beduidend minder van het geslachtshormoon testosteron aanmaakten. De andere studie onder vrouwen met het Polycysteus-ovariumsyndroom of PCOS (aantal samenhangende afwijkingen, waarbij vaak (kleine) cysten in de eierstokken aanwezig zijn) blijkt dat afhankelijk van het gewicht zij wel 30 tot 60% hogere bloedwaarden BPA hadden dan vrouwen zonder die aandoening. BPA is een chemische stof die wordt gebruikt voor de productie van polycarbonaat, een transparante plastic die onder andere gebruikt wordt als drager van CD's en DVD's en voor onbreekbare flessen voor (baby)voeding, voor tafelbestek, en voorwerpen voor gebruik in microgolfovens. Het wordt ook gebruikt in epoxyharsen die als beschermende coating aan de binnenkant van voedingsverpakkingen in blik of karton worden aangebracht, of in leidingen en reservoirs voor drinkwater. Bisfenol A wordt ook gebruikt in vlamvertragende middelen, ook in tandvullingen en als oplosmiddel voor drukinkten. Het is bewezen dat BPA kan vrijkomen uit de verpakking en in de voeding terechtkomt. Verschillende studies laten zien dat BPA mogelijke schadelijke effecten geeft zoals, hart-, vaatziektes, diabetes, prostaatvergroting, vruchtbaarheidsproblemen, vervroegde puberteit, hormonale problemen, gedragsstoornissen zoals hyperactiviteit, leerstoornissen, enz. Vooral bij jonge kinderen en baby's zouden deze effecten op termijn het grootst zijn.
Early-Life Exposure To BPA May Affect Testis Function In Adulthood
Exposure to environmental levels of the industrial chemical bisphenol A, or BPA, in the womb and early life may cause long-lasting harm to testicular function, according to a new study conducted in animals. The results were presented at The Endocrine Society's 92nd Annual Meeting in San Diego.
"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 Benson Akingbemi, PhD, the study's lead author and an associate professor at Auburn (Ala.) University. "This is concerning because large segments of the population, including pregnant and nursing mothers, are exposed to this chemical."
Many hard plastic bottles and canned food liners contain BPA, as do some dental sealants. BPA acts in a similar manner as the female sex hormone estrogen and has been linked to female infertility. This chemical is present in placenta and is able to pass from a mother into her breast milk. In their study of the male, Akingbemi and colleagues saw 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, Akingbemi explained.
The process of testosterone secretion was decreased 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. Akingbemi said this is below the daily upper limit of safe exposure for humans, which federal guidelines currently put at 50 micrograms per kilogram of body weight. 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 BPA.
Using a combination of analytical methods, the investigators studied the development of Leydig cells in male offspring. 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.
"Although BPA exposure stopped at 21 days of age, BPA's effects on Leydig cells, which were seen immediately at the end of exposure and at 35 days, remained apparent until 90 days of age, when the rats reached adulthood," Akingbemi said. "Therefore, the early life period is a sensitive window of exposure to BPA and exposure at this time may affect testis function into adulthood."
Funding from this study came in part from the Graduate Research Scholars Program of Alabama EPSCoR (Experimental Program to Stimulate Competitive Research), Tuscaloosa, Ala., and the National Institute of Environmental Health Sciences.

Source: Endocrine SocietyWomen With Polycystic Ovary Syndrome Have Higher BPA Blood Levels
Women with the polycystic ovary syndrome (PCOS), the most common hormone imbalance in women of reproductive age, may be more vulnerable to exposure to the chemical bisphenol A (BPA), found in many plastic household items, according to a new study. The results will be presented Sunday at The Endocrine Society's 92nd Annual Meeting in San Diego.
The study found that BPA, a known hormone disrupter, 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, MD, PhD, 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.
Excessive secretion of androgens masculinization-promoting hormones occurs in PCOS. The syndrome raises the risk of infertility, obesity, Type 2 diabetes and heart disease.
Past studies show that BPA is elevated in women who have had recurrent miscarriages. This chemical can leach into the bloodstream from food and beverage containers that are made of polycarbonate hard plastic or lined with epoxy resins, or from some dental sealants and composites.
In the new study, 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.
Additionally, 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 reported.
Although BPA is a weak estrogen, excessive secretion of androgens, as seen in PCOS, interfere with BPA detoxification by the liver, leading to accumulation of blood levels of BPA, Diamanti-Kandarakis explained.
"BPA also affects androgen metabolism, creating a vicious circle between androgens and BPA," she said.
Diamanti-Kandarakis said women with PCOS may want to limit their exposure to BPA.
"However," she said, "no one has proved that by reducing BPA levels in PCOS, it will have beneficial effects."
Source: Endocrine Society (September 2010)