快猫短视频

AMERICAN boys are going through puberty younger than ever, and black boys
earliest of all, says the researcher who discovered the same phenomenon in girls
in 1997. Though the team has no explanation for this, they fear that it could be
the result of changes in lifestyle and chemical pollutants.

Puberty is a gradual process of sexual development. In boys, it begins with
an increase in the size of the testes and penis and then by the growth of pubic
hair. The first sign for girls is breast development. 鈥淔or girls, it鈥檚 a public
event,鈥� says Marcia Herman-Giddens of the University of North Carolina at Chapel
Hill. 鈥淏ut for boys, it鈥檚 private鈥攕o private that the little boy himself
may not even know.鈥�

Much attention has been given to the study of puberty in girls, but there鈥檚
been relatively little interest in boys, she says. In a 1997 study,
Herman-Giddens found that not only were girls developing breasts and pubic hair
earlier, but African American girls were on average a year ahead of their white
counterparts.

To see if similar changes were happening in boys, Herman-Giddens and her team
analysed data from the US National Health and Nutrition Examination Survey III,
which took place between 1988 and 1994. In the survey, doctors looked for signs
of sexual development in 2114 boys aged from 8 to 19 years. The survey included
white boys, African Americans and Mexican Americans.

Sure enough, boys were also starting puberty at a younger age. Previous
studies pegged the onset of puberty for white boys at about 12.5 years. The new
study suggests that鈥檚 now 12 years鈥攁nd 11.2 years for black boys. However,
puberty finished only slightly earlier, suggesting that the process is taking
longer鈥攎irroring what Herman-Giddens found in American girls.

What鈥檚 causing this earlier onset of puberty is not clear. 鈥淚 think a lot of
it is environmental,鈥� Herman-Giddens says. Everything from the food a child eats
and the exercise he takes, to the amount of light he鈥檚 exposed to, can have an
effect. She is especially concerned about the possible role of endocrine
disruptors, such as pesticide residues
(快猫短视频, 19 May, p12).

Edward Reiter, a paediatric endocrinologist at the Baystate Medical Center
Children鈥檚 Hospital in Springfield, Massachusetts, says that you really need to
measure testicular volume to be sure that puberty has begun; a visual
inspection, as in the data Herman-Giddens used, is not enough. Nor is he
convinced that the 鈥渢empo鈥� of puberty has really changed. 鈥淲hereas the signs of
puberty may be earlier, the age of reproductive capability has not accelerated,鈥�
he says.