New developments in the ongoing mysteries of autism, and its seeming prevalence in boys....
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U.S. Department of Health and Human Services
NATIONAL INSTITUTES OF HEALTH NIH News
National Institute of Child Health and Human Development (NICHD)
FOR IMMEDIATE RELEASE: Friday, June 22, 2007
Boys with autism and autism spectrum disorder had higher levels of
hormones involved with growth in comparison to boys who do not have
autism, reported researchers from the National Institutes of Health, the
Centers for Disease Control and Prevention, the Cincinnati Children's
Hospital and the University Of Cincinnati College Of Medicine.
The researchers believe that the higher hormone levels might explain the
greater head circumference seen in many children with autism. Earlier
studies had reported that many children with autism have very rapid head
growth in early life, leading to a proportionately larger head
circumference than children who do not have autism.
The researchers found that, in addition to a larger head circumference,
the boys with autism and autism spectrum disorder who took part in the
current study were heavier than boys without these conditions.
"The study authors have uncovered a promising new lead in the quest to
understand autism," said Duane Alexander, M.D., Director of the National
Institute of Child Health and Human Development, the NIH institute that
funded the study. "Future research will determine whether the higher
hormone levels the researchers observed are related to abnormal head
growth as well as to other features of autism."
Autism is a complex developmental disorder that includes problems with
social interaction and communication. The term autism spectrum disorder
(ASD) refers to individuals who have a less severe form of autism.
The study was published on line in "Clinical Endocrinology".
The researchers compared the height, weight, head circumference and levels
of growth-related hormones to growth and maturation in 71 boys with autism
and with ASD to a group of 59 boys who did not have these conditions.
The investigators found that the boys with autism had higher levels of two
hormones that directly regulate growth (insulin-like growth factors 1 and
2). These growth-related hormones stimulate cellular growth. The
researchers did not measure the boys' levels of human growth hormone,
which for technical reasons is difficult to evaluate.
The boys with autism also had higher levels of other hormones related to
growth, such as insulin-like growth factor binding protein and growth
hormone binding protein.
In addition to greater head circumference, the boys with autism and those
with autism spectrum disorders weighed more and had a higher body mass
index (BMI). BMI is a ratio of a person's weight and height. A higher
BMI often indicates that a person is overweight or obese. The boys'
higher BMI may be related to their higher hormone levels, said the study's
principal investigator, NICHD's James L. Mills, M.D., a senior
investigator in the Division of Epidemiology, Statistics and Prevention
Research's Epidemiology Branch. Dr. Mills and his coworkers also found
that there was no difference in height between the two groups of boys.
The levels of growth-related hormones were significantly higher in the
boys with autism even after the researchers compensated for the fact that
higher levels of these hormones would be expected in children with a
greater BMI.
"The higher growth-related hormone levels are not a result of the boys
with autism simply being heavier," said Dr. Mills.
While it has long been noted that many children with autism have a larger
head circumference than other children, few studies have investigated
whether these children are also taller and heavier, Dr. Mills added.
Researchers analyzed medical records and blood samples from 71 boys
diagnosed with autism and ASD who were patients at Cincinnati Children's
Hospital Medical Center from March 2002 to February 2004. The researchers
compared the information on the boys with autism and autism spectrum
disorders to other boys treated for other conditions at the hospital and
who do not have autism. Children with conditions that may have affected
their growth -- such as being born severely premature, long-term illness,
or the genetic condition Fragile X were not included in the study. Girls
are much less likely to develop autism than are boys, and the researchers
were unable to recruit a sufficient number of girls with autism to
participate in the study.
Dr. Mills explained that the bone age of the boys with autism -- the bone
development assessed by taking X-rays and comparing the size and shape of
the bones to similarly-aged children -- were not more advanced in the
group of boys with autism. For this reason, Dr. Mills and his coworkers
ruled out the possibility that they were merely maturing more rapidly than
were the other boys.
Dr. Mills said that future studies could investigate whether the higher
levels of growth hormones seen in children with autism could be directly
related to the development of the condition itself.
The NICHD sponsors research on development, before and after birth;
maternal, child, and family health; reproductive biology and population
issues; and medical rehabilitation.
The National Institutes of Health (NIH) -- The Nation's Medical Research
Agency -- includes 27 Institutes and Centers and is a component of the U.
S. Department of Health and Human Services. It is the primary federal
agency for conducting and supporting basic, clinical, and translational
medical research, and it investigates the causes, treatments, and cures
for both common and rare diseases. For more information about NIH and its
programs, visit <http://www.nih.gov>.
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