Padded bras for kindergarteners [3] with growing breasts to make them more comfortable? Sixteen percent of U.S. girls experiencing breast development by the age [4] of 7? Thirty percent by the age of 8? Clearly something is affecting the hormones of U.S. girls—a phenomenon also seen in other developed countries. Girls in poorer countries seem to be spared—until they move [5] to developed countries.

No scientists dispute that precocious or early-onset puberty is on the rise but they do not agree on the reasons. Is it bad diets and lack of exercise that cause growing obesity? Is it soft drinks [6] themselves, even when not linked to obesity? Is it the common [7] chemicals [8] known as endocrine disrupters that exert estrogen-like effects (and also cause obesity)? Is it the many legal, unlabeled hormones used in the U.S. to fatten livestock [9]? Some researchers even believe precocious puberty could be triggered by sociological factors like having no father [10] in the home or even stress. [6]

Puberty in girls is defined by three [5] things: breast development (thelarche), appearance of pubic hair (pubarche) and the onset of menstrual periods (menarche), the latter coming last. In the 1700s, girls did not menstruate until [11] age 17 or 18, and 100 years ago the average age when a girl got her first period was [12] 16-17.

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