|Boys with Autism, Related Disorders, Have High
Levels of Growth Hormones
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
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
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. For more information, visit
the Institute’s Web site at http://www.nichd.nih.gov/.
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 www.nih.gov.