In the west, in the past forty years, it is also a trend for girls to develop their breasts ahead of schedule. A study on 6 10 American girls was published in the 20 14 international journal of pediatric endocrinology (j pedia trendinol metab.2014; 27:47) It is reported that the breast development age of American girls has also dropped to 9.7 years. If normal within two standard deviations, the normal range of breast development age is 7.4- 12.0. The nation has a certain influence. The breast development of African-American girls is 0.7 years ahead of schedule. Interestingly, the age of menarche has not changed much, and it is still 12.8 years old. The same is true in Europe. A study from Denmark reported that the age of girls' breast development dropped by one year in fifteen years, from 199 1 to 10.8 years in 2006 (pediatrics. 123:e32).
In addition to good nutrition and children gaining weight, parents will naturally ask whether it is related to environmental pollution or hormones added to food. The Danish study compared the estrogens (estrogen, luteinizing hormone) of girls with well-developed breasts and found that there was no difference between the two groups. Let's just say that we can't determine the reason at present.