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September 25 , 2000
News this month
Changing the definition of early puberty
Is pubertythe onset
of sexual developmentstarting earlier in girls? Yes, according
to evidence reported in two related articles in the journal Pediatrics.
Breast development is the most reliable milestone used to mark the
beginning of puberty. Research is showing that Caucasian girls are
developing breasts and pubic hair about a year earlier than previously
thought, with African-American girls developing two years earlier.
The findings have broad medical implications for what is considered
"normal" development in girls, including whether those
undergoing early puberty should be given drugs to slow its progression.
It also raises social issues, from deciding to begin sex education
earlier in public schools to dealing with anxious parents concerned
about their daughters appearance.
Nearly half (48.3%) of African-American girls and
14.7% of Caucasian girls had begun development by age eight.
Study shows earlier development
In 1997, Marcia Herman-Giddens and her colleagues noted in the April
issue of Pediatrics that girls across the United States were
developing breasts and pubic hair at younger ages than previously
reported. In all, 17,077 girls were studied, of whom 9.6 percent were
African-American and 90.4 percent were Caucasian. At age three, 3
percent of African-American girls and 1 percent of white girls showed
breast and/or pubic hair development. By seven, the numbers jumped
to 27.2 percent for African-American girls and 6.7 percent for Caucasian
girls. Nearly half (48.3 percent) of African-American girls and 14.7
percent of Caucasian girls had begun development by age eight.
Herman-Giddens and her colleagues concluded that practitioners might
need to lower the age now considered normal for development, paying
attention to racial differences. Early puberty can be delayed with
injections of the drug Lupon, but doing so has raised many ethical,
social and health questions.
Redefining normal
The Herman-Giddens study showed a significant drop in the age at which
puberty began in girls compared to earlier studies. Research done
in the 1940s and 50s, for example, showed average breast bud development
beginning at about age 10½. In 1969, the earliest age was down to 8½ years, when W.A. Marshall and J.M. Tanner reported "the first
sign of puberty appeared between the ages of 8.5 years and 13 years
in 95 percent of girls."
The Tanner study was extremely influential and pediatricians since
have relied on the Tanner stages of development to define what is
normal development in girls. Girls who develop very early or very
late can be referred for a medical evaluation by a specialist.
Further support for new data
But when is a referral necessary? Age 7? Age 8? The Lawson Wilkins
Pediatric Endocrine Society reviewed the Herman-Giddens study in depth
and reported:
- Girls with either
breast development or pubic hair should be evaluated only
if this occurs before age 7 in white girls and before age 6 in
African-American girls.
- Guidelines to treat
girls who had breast development before age 8 were based on old
data.
- Concerns that girls
undergoing early puberty will be significantly short adults are
overstated.
The Herman-Giddens study has its critics. . .doctors
warned its potentially dangerous to assume the start of puberty
is normal at these ages.
Critics have their say
The Herman-Giddens study has its critics. In the July 2000 Pediatrics,
British researcher Fiona Finlay suggested that a more randomized study
be conducted before age guidelines are changed. In the January issue
of Pediatrics, and again in September, doctors warned its
potentially dangerous to assume the start of puberty is normal at
these ages. So that potentially serious underlying medical issues
are not overlooked, they recommend comprehensive evaluation in such
girls.
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Is puberty
starting earlier in girls?
The Herman-Giddens
study is probably attracting more attention now than it did three
years ago when it was published. I wrote a commentary on the study
that appeared in that same issue, noting that sexual development
has long been far more variable in children than suggested in standard
textbooks. Thats something for everyone to keep in mind.
"
sexual development has long been far more variable in
children than suggested in standard textbooks."
Textbooks v. reality
Conventionally, people have thought of children as maturing close
to their teenage years, with girls maturing earlier than boys. Textbooks
have long stated that girls begin to develop breasts after age 8 and
pubic hair after age 9. The milestone for female sexual development
is the first menstrual period, which occurs at about 11 or 12 years
old. The average age of the first period has not changed much over
time.
"
if something is happening in half of the girls, it is
not abnormal."
What the Herman-Giddens study recorded, however, is that these ages
in the textbooks are probably not a reflection of what is actually
happening. By age 8, 15 percent of Caucasian girls had started development
and almost half of African-American girls had realized stage 2 development.
The point is that if something is happening in half of the girls,
it is not abnormal. Why there is such a difference between African-American
girls and Caucasian girls is not clear, but its a gap of about
18 months.
When is medical intervention necessary?
The whole point of this discussion is that parents and physicians
need to know at what point is the appearance of sexual development
abnormal and worthy of further medical investigation. For example,
I would recommend that any child six or younger showing signs of development
be evaluated by an experienced specialist in pediatric endocrinology.
At any age, if parents are concerned, it is certainly always worth
a few simple medical tests to rule out any underlying medical problems.
"
any child six or younger showing signs of development
[should] be evaluated
"
The connection between obesity and development
Were
not sure why this trend is happening, but we do know that obesity
can bring on earlier puberty and there is certainly more obesity in
children than ever before. At Yale we are seeing more young female
patients who are overweight and have earlier sexual hair development,
which is linked to the production of certain hormones. These girls
characteristically also tend to be taller for their age. This subset
of girls is at risk for polycystic ovarian disease and diabetes later
in life and intervention is not easy.
Determining when to act
There has long been a concern that early puberty that progresses too
quickly can lead to shortened height in adulthood, but that was not
shown to be the case in the Herman-Giddens study. To determine if
puberty is advancing too fast, we use a bone age test, which uses
X-rays to obtain an image of the bones in a girls hand. As children
age, the bone plates in the hand begin to close. We compare her hand
to the standard for her age.
Ideally, her bone age should be no more than two years more than her
chronological age. Otherwise, her growth plates might be closing too
rapidly and her adult height might be compromised. If so, we might
consider an injection with a modified hormone once a month that stops
the progression of puberty until real age catches up with bone age.
There are other types of tests and treatments, but all must be administered
under the guidance of an expert in the field with the side effects
in mind.
Treating for appearances
Would I treat a child who was otherwise healthy simply to stop early
but in all respects normal puberty? You encroach on cosmetic endocrinology
when considering treatment simply for the sake of the childs
appearance rather than medical need. I would not preclude that as
an option, but its something to be considered only after weighing
all the options.
Myron Genel, MD,
is professor of pediatrics, associate dean at Yale School of Medicine
and a pediatric endocrinologist affiliated with Yale-New Haven Childrens
Hospital.
Yale-New Haven
was recognized this year by U.S. News & World Report for
its pediatric services.
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