Lakhasly

Critical Analysis of the Relationship between Bisphenol A (BPA) and Puberty
The first data on BPA and puberty was obtained from studies conducted on animals. A growing number of animal experiments, especially on rats, has highlighted that early puberty onset may be caused by exposure to BPA in the female population [343-347],. Other studies have published results that are inconsistent with these data, in particular those referring to BPA exposure in utero and during breastfeeding. However, other studies on rats have shown no clear correlation with puberty early onset, even among works evaluating postnatal exposure to BPA.
Among the limited number of human studies, similar equivocal results have been found. Only 7 of the 19 scientific articles considered in this review showed a correlation between BPA and pubertal development. Surveys that evaluated female patients with central precocious puberty and isolated premature breast development aged 2 months to 4 years have confirmed that early exposure to EDCs may lead to risk of developing signs of early puberty. However, a direct relationship between BPA levels and age of menarche or pubertal stage has not been found. The reason for the elevated serum or urine values of BPA in children affected by central precocious puberty has not yet been explained.
The underlying molecular mechanism is not clear: only 2 studies evaluated serum levels of kisspeptin, and both found no association with BPA levels. This might suggest that BPA action on precocious puberty plays a different role towards the activation of kisspeptin’s network. In fact, even if an indirect action of BPA on puberty through interference with the GnRH axis is possible, some studies have ruled out any correlation between blood levels of BPA, FSH, LH, and oestradiol. However, the possibility of identifying elevated levels of BPA in obese or overweight girls is accepted as is the possible obesogenic effect of exposure to BPA and the close relationship between urinary BPA, body weight, and early puberty . Another consideration can be made about Wang’s study in Chinese boys, as a delay in sexual development was found. This result seems to confirm the idea that children with premature pubertal onset undergo a compensatory slowdown in the late-pubertal stage.
The data obtained from surveys are conflicting, perhaps because of the lack of standardization of studies. A further explanation might be the different geographical areas where the epidemiological investigations have been carried out. The most studied populations were in America and Asia, in 5 and 13 papers, respectively. None of the American studies found an effect of BPA on puberty, whereas 7 of the 13 Asian studies found a correlation. The different exposures based on geographic location can probably explain this difference. Furthermore, different pathological expressions resulting from exposure to EDC can be suspected in various human ethnic groups [351]. The association between BPA and early puberty could reflect changes in personal habits, such as familiar and socio-economic conditions or variable pharmacokinetics and metabolism that are difficult to quantify. Zawatski and Lee have advanced another hypothesis for the conflicting results: EDCs show non-monotonic dose-response relationships instead of the fluctuation of hormone levels during pubertal transition; thus, measurements cannot be considered representative of the hormonal condition. In the end, the different results of epidemiological studies may be attributed to the various methods used for the determination of BPA exposure. Regarding BPA metabolism, it has a short half-life (5–6 h) in our bodies and is almost completely eliminated after 24 h .Regarding urinary BPA determinations, several studies have demonstrated that single spot samples of urine give an average value of prolonged exposure to such EDCs. Teitelbaum stated that single measurements of urinary phenols are fairly representative of 6–12 months of exposure in children. Another advantage of BPA urinary determination is the easy detection (more than 90% of the general population, according to some studies).