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GIRLS ARE REACHING PUBERTY EARLY
I've heard that girls are reaching puberty early, but this is
ridiculous. I entered puberty at age 10; most of my friends, age 11.
That was in the 1950's. Now, some girls are entering at age 3! Will my
daughter's grandchildren (if they are allowed to be conceived and
carried to term) be born into puberty? ...Bunny Snow
. RACHEL'S ENVIRONMENT & HEALTH WEEKLY #566 .
. ---October 2, 1997--- .
. HEADLINES: .
. GIRLS ARE REACHING PUBERTY EARLY .
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GIRLS ARE REACHING PUBERTY EARLY
Many girls in the U.S. are entering puberty much earlier than
normal, according to a recent study reported in the journal
PEDIATRICS. And there is some evidence that exposure to
environmental chemicals many be contributing to the phenomenon.
Current medical texts say that only 1% of girls show signs of
puberty, such as breast development and pubic hair, before the
age of 8. But the PEDIATRICS study found that a substantial
proportion of American girls have one or both of these
characteristics at age 7 and that 1% of all girls now have one or
both of them at age 3.
Data for the study were collected by 225 physicians in suburban
practices who recorded the physical growth of 17,077 of their
young female patients, of whom 90.4% were white and 9.6% were
African-American. The authors of the study say their sample
of girls was not selected randomly and therefore may not
accurately represent the entire U.S. population of female
children. However, they know of no systematic bias in their
sample and they believe the girls they studied are typical.
The early onset of puberty was observed in both white and
African-American girls, but with significant differences between
them. African-Americans showed the first signs of sexual maturity
about a year earlier than whites. Previous studies had observed
these racial differences, but no one has provided an explanation
for them. (There is some evidence that these racial
differences have developed only recently. A 1944 study
reportedly found no such differences.)
The new PEDIATRICS study found that, at age 7, 27.2% of
African-American girls, and 6.7% of white girls had either breast
or pubic hair development; by age 8, 48.3% of African-American
girls and 14.7% of white girls had one or both of these
characteristics. The study also found that 1% of whites and 3%
of African-Americans had such characteristics at age 3.
The study found that the average age for onset of puberty was
just under 9 for African-Americans and was 10 to 10 1/2 for
whites. Current medical texts say puberty begins between the
ages of 11 and 12, on average.
The authors say it is conceivable that their sample might have
been biased by young girls entering puberty whose parents became
concerned and sent them for medical examination. If so, they
said, an equivalent parental concern should produce, in their
sample, an excess of 12 year olds who show no development, but no
such excess appeared in the data.
The study found that age of first menstruation has not changed.
Average age of first menstruation in whites is 12.8 years and in
African-Americans is 8 months earlier. This is a pattern that
has held steady for 30 or 40 years, the authors say.
The principal author of the study, Dr. Marcia E. Herman-Giddens
told the NEW YORK TIMES, "The reason I did this study is that in
my clinical practice, I was seeing a lot of young girls coming in
with pubic hair and breast development, and it seemed like there
were too many, too young. But I don't think any of us expected
to see such a large proportion of girls developing this early,"
she said. Dr. Herman-Giddens is an adjunct professor of
maternal and child health at the University of North Carolina
(Chapel Hill) School of Public Health.
The PEDIATRICS study suggests that environmental chemicals that
mimic estrogens might be involved. The authors point to a small
study of 10 girls who entered puberty early as a result of
exposure to hair-care products that had estrogenic properties.
They suggest that other well-known estrogenic chemicals, such as
PCBs (polychlorinated biphenyls) should be studied to see if they
are implicated in early-onset puberty.
As it happens, a very recent preliminary report indicates that
PCBs and DDE (a breakdown product of the pesticide DDT) may
indeed be associated with early sexual development in girls.
Both DDE and PCBs are known to mimic, or interfere with,
According to the British journal NEW SCIENTIST, Dr. Walter Rogan
described preliminary data at a conference on environmental
estrogens in July in Arlington, Va. Rogan is acting clinical
director at the U.S. National Institute of Environmental Health
Sciences (NIEHS) in Research Triangle, North Carolina.
According to NEW SCIENTIST, between 1979 and 1982 Rogan and his
colleagues measured PCBs and DDE in blood and breast milk of
hundreds of pregnant women in North Carolina. They also measured
the chemicals in fetal blood collected from umbilical cords after
birth. They then monitored the physical growth and maturity of
600 of the children of these women. According to NEW SCIENTIST,
girls with the highest pre-natal exposures to the chemicals
entered puberty 11 months earlier than girls with lower
exposures. For boys, exposures to the chemicals before birth
made no apparent difference in sexual development.
Rogan minimizes the importance of his data, but others say his
findings are significant because few studies have ever looked at
chemical effects on the offspring of exposed women, and the women
Rogan studied were exposed to PCBs and DDE from normal diet and
environmental sources, not from industrial accidents of other
abnormally high exposures.
Is there other evidence that estrogen-mimicking chemicals could
speed up the sexual maturation of mammals? At least three
laboratory studies seem relevant here:
** Female rats were fed a diet that contained a phytoestrogen (a
naturally-occurring plant that mimics estrogen). The ovulation
of their offspring was prematurely terminated --a sign that their
sexual development had been speeded up by their mother's diet.
** Exposing immature female mice to high levels of methoxychlor
stimulated them to early sexual maturity. Methoxychlor is
currently used in this country as a substitute for DDT which was
banned in the 1970s, partly because of its estrogenic properties.
The estrogenic properties of methoxychlor have become
well-established in recent years, but its use continues.
** Rats treated once with certain PCBs on the second or third day
of life exhibited a permanent alteration in sexual development.
Specifically, young female rats treated once with Monsanto's
Arochlor 1221 (a PCB) achieved sexual maturity in 28 days whereas
untreated controls reached sexual maturity in 42 days.
The authors of the PEDIATRICS study wrote, "This study strongly
suggests that earlier puberty is a real phenomenon, and this has
important clinical, educational, and social implications."
As the authors of the pediatrics study hint, the clinical
implications may be serious. The arrival of puberty is driven by
naturally-occurring estrogenic hormones coursing through the
blood stream. There is now considerable evidence that breast
cancer is promoted by the presence of these same
naturally-occurring estrogens. Women who go through puberty early
have a longer-than-normal exposure to these estrogens and
therefore may be in greater danger of getting breast
Breast cancer now kills 46,000 American women each year and the
number is steadily rising; the reasons for the rise are poorly
understood but there is widespread agreement that estrogen plays
a role in the disease. In recent years, researchers have
hypothesized that environmental chemicals that mimic estrogens
may also promote breast cancer.
The social implications of early-onset puberty are obvious: young
children with mature bodies must cope with feelings, urges and
differences from their peers that most children are not
well-equipped to handle. For many children, early pubescence may
be a significant burden to bear.
(National Writers Union, UAW Local 1981/AFL-CIO)
 Marcia E. Herman-Giddens and others, "Secondary Sexual
Characteristics and Menses in Young Girls Seen in Office
Practice: A Study from the Pediatric Research in Office Settings
Network," PEDIATRICS Vol. 99, No. 4 (April 1997), pgs. 505-512.
 G. Bacon and others, A PRACTICAL APPROACH TO PEDIATRIC
ENDOCRINOLOGY (Chicago: Year Book Medical Publishers, 1982), pg.
189. Current ideas about normal age of puberty are derived from
studies such as: W.A. Marshall and J.M. Tanner, "Variations in
Pattern of Pubertal Changes in Girls," ARCHIVES OF DISEASES OF
CHILDHOOD Vol. 44 (1969), pgs. 291-303; Peter A. Lee, "Normal
Ages of Pubertal Events Among American Males and Females,"
JOURNAL OF ADOLESCENT HEALTH CARE Vol. 1 (1980), pgs. 26-29;
Arline B. Nicholson and Charles Hanley, "Indices of Physiological
Maturity: Derivation and Interrelationships," CHILD DEVELOPMENT
Vol. 24, No. 1 March 1953), pgs. 3-38; and Earle L. Reynolds and
janet V. Wines, "Individual Differences in Physical Changes
Associated With Adolescence in Girls," AMERICAN JOURNAL OF
DISEASES OF CHILDREN Vol. 75 (1948), pgs. 329-350.
 For example see, William R. Harlan and others, "Secondary sex
characteristics of girls 12 to 17 years of age: The U.S. Health
Examination Survey,"JOURNAL OF PEDIATRICS Vol. 96, No. 6 (June
1980), pgs. 1074-1078.
 See Leona Zacharias and Richard J. Wurtman, "Age at
Menarche," NEW ENGLAND JOURNAL OF MEDICINE Vol. 280, No. 16
(April 17, 1969), pgs. 868-875, describing results reported in N.
Michaelson, "Studies in physical development of Negroes. IV.
Onset of puberty," AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY Vol.
2 (1944), pgs. 151-166.
 Susan Gilbert, "Early Puberty Onset Seems Prevalent," NEW
YORK TIMES April 9, 1997, pg. 10.
 Chandra M. Tiwary, "Premature sexual development in children
following the use of placenta and/or estrogen containing hair
product(s)," PEDIATRIC RESEARCH Vol. 135 (1994), pg. 108A.
 William R. Kelce and others, "Persistent DDT metabolite
p,p'-DDE is a potent androgen receptor antagonist," NATURE Vol.
375 (June 15, 1995), pgs. 581-585.
 James D. McKinney and Chris L. Waller, "Polychlorinated
Biphenyls as Hormonally Active Structural Analogues,"
ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 102, No. 3 (March 1994),
 Nell Boyce, "Growing up too soon," NEW SCIENTIST August 2,
1997, pg. 5.
 Patricia L. Whitten and others, "A Phytoestrogen Diet
Induces the Premature Anovulatory Syndrome in Lactationally
Exposed Female Rats," BIOLOGY OF REPRODUCTION Vol. 49 (1993),
 Laura M. Walters and others, "Purified Methoxychlor
Stimulates the Reproductive Tract in Immature Female Mice,"
REPRODUCTIVE TOXICOLOGY Vol. 7 (1993), pgs. 599-606.
 Ronald J. Gellert, "Uterotrophic Activity of Polychlorinated
Biphenyls (PCB) and Induction of Precocious Reproductive Aging in
Neonatally Treated Rats," ENVIRONMENTAL RESEARCH Vol. 16 (1978),
 B.A. Stoll and others, "Does early physical maturity
influence breast cancer risk?" ACTA ONCOLOGICA Vol. 33, No. 2
(1994), pgs. 171-176.
 D. Apter, "Hormonal events during female puberty in
relation to breast cancer risk," EUROPEAN JOURNAL OF CANCER
PREVENTION Vol. 5, No. 6 (1996), pgs. 476-482.
 Eliot Marshall, "Search for a Killer: Focus Shifts from Fat
to Hormones," SCIENCE Vol. 259 (January 29, 1993), pgs. 618-621.
 Devra Lee Davis and H. Leon Bradlow, "Can Environmental
Estrogens Cause Breast Cancer?" SCIENTIFIC AMERICAN Vol. 273, No.
4 (October, 1995), pgs. 166-172.
Descriptor terms: child development; estrogens; hormone
disrupters; endocrine disrupters; hormones; dde; pcbs;
african-americans; studies; pediatrics; ddt; walter rogan;
methoxychlor; phytoestrogens; arochlor 1221; breast cancer;
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