O período médio em que ocorre a menarca ocorre, aos 12 anos, (nos EUA, em países tropicais parece que é um pouco antes) tem estado estável durante alguams décadas. O desenvolvimento dos seios baixou de 10.88 anos para 9.86 anos entre 1991 e 2006, sendo que 13 porcento das meninas já começaram o "segundo estágio" de desenvolvimento dos seios aos 7 anos. Menarca precoce está associada com maior chance de desenvolvimento de câncer de mama.
As possíveis explicações vão desde de hormônios ambientais, relacionamento com os pais, cultura infantil erotizada, padrões de alimentação, até talvez alimentação
das mães durante a gestação.
As increasingly early puberty ups breast cancer risk, researchers search environment for clues
[...]
Both puberty and breast cancer are linked to increased levels of estrogen, and as research reveals more about estrogen-mimicking compounds (a group of endocrine disruptors that includes bisphenol-A and phthalates), some doctors and advocates are drawing more connections among the chemicals, our reproductive developmental phases and the disease.
These common compounds, which can thwart normal cell communications about growth and metabolism, have been a popular target of environmental health advocates campaigning against a variety of ills—from behavioral problems to reproductive issues—but they are gaining popularity in the breast cancer research field. Both the National Cancer Institute and the American Cancer Society, however, note that environmental factors such as these have yet to be proven as risk factors for breast cancer.
Research on bisphenol-A (or BPA, commonly found in some plastics and canned goods) and phthalates (present in many personal care products and some food packaging) has shown that these classes of chemicals are common throughout the population, with the highest levels in children ages 6 to 11. These findings have led some in the field, such as Maida Galvez, an assistant professor of preventive medicine at Mount Sinai, to posit that endocrine disruptors such as bisphenol-A and phthalates might have a role in lowering the age of puberty in girls.
[...]
http://www.scientificamerican.com/blog/post.cfm?id=as-increasingly-early-puberty-ups-b-2009-11-30
New study suggests link between environmental toxins and early onset puberty in girls
Cincinnati, February 6, 2008 – Although scientists have speculated over the negative effects of environmental toxins for years, new data suggest that certain environmental toxins may disrupt the normal growth and hormonal development of girls. Some of these toxins, such as the mycoestrogen zearalenone (ZEA) produced by the Fusarium fungus species, can be found naturally in the environment, have properties similar to the female reproductive hormone estrogen, and are also structurally similar to anabolic growth agents used in animal breeding. A new study scheduled for publication in The Journal of Pediatrics suggests that certain mycoestrogens may be directly linked to the early onset of sexual development in young girls. [...]
http://www.eurekalert.org/pub_releases/2008-02/ehs-nss020608.php
Age At Puberty Linked To Mother's Prenatal Diet
ScienceDaily (June 17, 2008) — A high-fat diet during pregnancy and nursing may lead to the child having an early onset of puberty and subsequent adulthood obesity, according to a new animal study. The results were presented June 16, at The Endocrine Society's 90th Annual Meeting in San Francisco. [...]
http://www.sciencedaily.com/releases/2008/06/080616151748.htm
Pouca coisa vi sobre como esses fatores ambientais estariam afetando os homens. Há alguns anos vi um documentário sobre um estudo japonês que detectou que os testículos vinham diminuindo ao longo das gerações. Especulação pura: será que o crescimento do metrossexualismo, "emo" e etc, poderiam ter uma espécie de gatilho ou nicho biológico, relacionado a isso?
Tópico: Puberdade das meninas começa cada vez mais precocemente (Lida 489 vezes)