Our Stolen Futurea book by Theo Colborn, Dianne Dumanoski, and John Peterson Myers
 
 

 

 

Is puberty occurring earlier in American girls, and if so, why?

When Marcia Herman-Giddens and colleagues published their landmark study in 1997 about a reduction in the age of puberty among American girls, alarm bells went off in the public and in the media. Based on thousands of girls around the country, the study suggested that black and white American girls were reaching puberty on average as much as a year earlier than expected based on historical data. The study reinforced anectodal reports and public impressions that girls were maturing earlier, sometimes much earlier, than usual. Parents and the press raised questions about why it was happening and what might be the consequences. Time Magazine, for example, ran a cover story, "Teens before their time."

Not only did the average age of puberty appear to be decreasing, but significant numbers of girls were maturing sexually long before the average. For example, Herman-Giddings' work revealed that by age 8, 48% of black girls and almost 15% of white girls were showing signs of sexual development.

Herman-Giddens' work stimulated great public interest. It has met with several responses:

  • Some people have challenged the basic finding. The principal criticisms of Herman-Giddens et al. are (1) that historical data are insufficient to allow a comparison; and (2) that the sample used in the study is not a random sample of the population. Instead it is composed disproportionately of children brought to see a pediatrician.
  • Some pediatricians have recommended that medical standards be revised so that girls developing at the average rate described by Herman-Giddens et al. be considered normal. This recommendation has been challenged by others, who argue (1) that there is insufficient proof of a change in rate of sexual development, (2) that changing the standards would make it less likely that girls needing medical intervention because of physiological problems would receive appropriate medical care; or (3) that changing the standards then undermines efforts to identify the causes of changes, if they are occurring.
  • Considerable attention has focused on what factors might be causing the changes, if they are real. The three leading hypotheses are (1) increases in the prevalence of obesity; (2) changes in social factors, particularly the absence of the biological father in the home and the presence of a male other than the biological father; and (3) contamination effects, particularly in the womb.

 

There are no certain answers on any of these issues.

On causation: data support each of the leading hypotheses. It may be that all are involved, or it may be that some cases (for example the case of premature thelarche in Puerto Rican girls) have one cause, others another (e.g., PBBs causing early menarche in Michigan).

The case for contamination affecting sexual development in animals is very strong, as is documentation of human exposure to those very contaminants. An additional complication is that, at least in laboratory animals, there is evidence that contamination can contribute to obesity.

On methodological criticisms: While Herman-Giddens et al.'s methodology can be criticized, their study cannot be dismissed out of hand. In response to criticisms about potential bias in the sample, Herman-Giddens replies that "although the subjects were not randomly selected and, therefore, might not be representative of the population at large...the large number of girls studied would make it unlikely they were different from the population as a whole." And while Herman-Giddens et al. do not address this in their response to criticisms, even if the average age of pubertal development has not changed, it is important to understand why such a notable percentage of very young girls are showing signs of sexual development.

On changing medical standards: Some of the criticisms suggested that Herman-Giddens et al. were arguing that the change meant that younger age of puberty should then be regarded as normal, and as not meriting medical intervention. This was one of the complaints conveyed by a confused pair of articles written by Gina Kolata in the New York Times in late February, early March 2001. To the contrary, Herman-Giddens et al. were not recommending a change in medical standards. They are concerned that young women developing early not be subjected inappropriately to unnecessary medical intervention, but that both the causes of the trend they discovered be identified and individual cases be addressed appropriately by medical professionals.

For example, in the March 2001 issue of Pediatrics, Herman-Giddens et al. review a case history in which a group of pediatricians report that a young woman showing early development did not receive an evaluation because her development fell within the pattern of the 1997 Herman-Giddens study. Herman-Giddens et al. respond by stating first that by their criteria, in fact the girl in question should have been evaluated. They then observe that "we are concerned that our study may be used inappropriately to deter clinicians from referring girls with very early puberty if the findings of our study are not carefully reviewed."

 

Rosenfield, RL et al. 2000. Current age of onset of puberty. Letter to the Editor. Pediatrics.

Herman-Giddens, ME et al. 2000. In reply. Pediatrics

Herman-Giddens, ME et al. 2001. Early puberty: a cautionary tale. Letter to the Editor. Pediatrics.

Kolata, Gina. Doubters Fault Theory Finding Earlier Puberty. New York Times. 20 February 2001.

Kolata, Gina. 2 Endocrinology Groups Raise Doubt on Earlier Onset of Girls' Puberty. New York Times 3 March 2001.

 

 

 

 

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