After analyzing data collected from over 17,000 American girls, Marcia Herman-Giddens, P.A., Dr. PH., concluded from her study in the April 1997 issue of Pediatrics that the age of onset of puberty for white and black girls is currently 9.7 and 8.1 years respectively. Herman-Giddens showed that puberty onset begins much earlier than the accepted norm of 11 years established in the 1960s. Many Americans have grown concerned that sexual development is occurring in younger girls and are actively searching for a cause.
But, before vilifying a potential cause for precocious puberty, we must be sure that the phenomenon exists. In order for researchers to show an earlier onset of puberty, they must get reliable developmental data pertaining to girls in the present and past.
Herman-Giddens measured sexual characteristics in modern girls. Her subjects, however, all visited participating pediatric practices and thus did not constitute a random sample. Likewise, the data from the past come from Marshall and Tanner’s research, which examined only girls at a British orphanage. Their data were not derived from a random sample either and thus cannot be used as a reliable norm reference to Herman-Giddens study.
Further, according to Herman-Giddens, while some secondary sexual characteristics — namely pubic hair and breast development — occur earlier in girls, the age of menarche (the first menstrual period) has remained constant for the past 40 years in white girls and has decreased by only a year in black girls. This data suggests that puberty is becoming a longer process that starts — but is not completed — earlier.
Despite a lack of certainty behind the occurrence of precocious puberty in girls, activists point disapproving fingers at a number of chemical and environmental factors they claim are likely causes of the hormonal abnormalities responsible for premature sexual development. In fact, last week Environmental Media Services (EMS) hosted a conference in Washington, D.C., searching for causes of early puberty. Speakers at the conference identified possible causes ranging from obesity to number of males in a household.
Not surprisingly, at the top of conference’s list of probable causes were environmental chemicals called phthalates. Phthalates have long offended the ideologies of many environmentalists. Associating phthalates with precocious puberty appears to be the latest attempt of activists to force unnecessary regulations on safe and beneficial chemicals. Phthalates are used as softeners in plastics allowing for the production of products ranging from medical devices to nail polish.
EMS speakers label phthalates as “endocrine disruptors,” exogenous chemicals that interfere with the synthesis or function of hormones. However, epidemiological data fail to support phthalates’ supposed adverse effects in humans. While some assert that “endocrine disruptors” act as estrogenic mimics to promote earlier development, there is no evidence to support this theory.
If puberty in girls is in fact starting earlier than in the past, the cause is likely a combination of biological, psychological and environmental factors. Obesity is the most significant factor in the opinion of most scientists because heavier girls usually reach puberty earlier than smaller girls. Since obesity in young girls is on the rise in the United States, it should receive the bulk of our attention, rather than chemicals with contrived associations with precocious puberty.
Until further research shows a causal relationship to sexual development, nothing is gained by avoiding chemicals and products otherwise known to be safe and, in the case of phthalates, beneficial. Anguishing over putative environmental chemical effects points concerned parents in the wrong direction. They would do their daughters more good by helping them stay active and slim.
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