studying factors affecting the pace of sexual development have identified
a variety of factors that can alter the timing of puberty. While
solid data exist demonstrating links between people and several
of these causes, those data address what has happened to small groups
of people (or individuals). As yet we lack strong evidence linking
any of them to widespread changes in the timing of puberty.
Many studies have revealed links between nutritional status, weight
and the timing of sexual development, from work documenting early
puberty in obese women (Zacharias
et al. 1970) to delayed puberty in thin ballet dancers
and McArthur 1974). The single best predictor for the onset
of menarche is weight, which is approximately 106 pounds when menarche
et al. 1992).
the causal mechanisms are far from complete resolution, it appears
that a recently discovered hormone, leptin, is involved. Puberty
can be advanced experimentally in mice by increasing leptin levels
al. 1997). Leptin links puberty to obesity because leptin
is secreted in fatty (adipose) tissue... more adipose tissue leads
to more leptin, which (according to these mouse studies) then triggers
earlier puberty. Measurements of obese people indicate they have
more leptin circulating in their blood.
of the complications of this hypothesis is determining what is causing
the changes in obesity patterns which in turn (by this hypothesis)
are driving the changes in puberty. Many causes have been cited,
including life style changes --more fast food, less walking, etc.
There are biological reasons, including data from animals, that
suggest contamination may also be involved by interfering with leptin's
role in weight regulation.]
Much research has focused on the impact on sexual development of
the family environment in which a girl is growing up. Some studies
examine the relationship between mother and daughter in affecting
the timing of the daughter's sexual maturation. Others have looked
at the impact of the father. One finding is that girls growing up
in stressed families reach puberty earlier (Moffitt
et al. 1992).
of girls growing up in families indicate that if the father is absent
or if an adult male who is not the girl's father is present, puberty
will occur earlier (Ellis
and Garber 2000).
wisdom--but no data--suggest that the increasingly overt sexuality
of popular media may stimulate earlier sexual development.
A wealth of data from experiments
with animals show that the rate of sexual development is vulnerable
to various contaminants, contaminants to which people are widely
exposed. Some epidemiological
studies and case histories in the medical literature indicate
sexual development in people also can be affected by contamination.
are also available linking human exposure to contaminants to
earlier puberty. Some of these studies come from epidemiological
work with exposed populations. Others are from case histories in