The latest in a series of studies on secretin has failed to show that giving the digestive hormone to children with autism alleviates symptoms of the disorder, according to a study funded by the National Institute of Child Health and Human Development.
The study, which appeared in the November 2001 issue of the Journal of the American Academy of Child and Adolescent Psychiatry, found that patients with autism who received a form of the hormone derived from swine showed no statistically significant improvements in the core symptoms of the disorder when compared to when the same patients received a placebo. (The core symptoms of autism involve social and communications skills.) In certain secondary measures of autism, patients receiving secretin also showed no improvement when compared to when they received a placebo.
The researchers used porcine secretin, a form of the hormone derived from pigs, and the form most commonly used in diagnostic tests of the digestive system. Previous studies have also tested laboratory manufactured secretin as a treatment for autism. The current study tested porcine secretin to rule out the possibility that the naturally occurring form of the hormone might have a different effect than does the synthetic version.
"These results, in addition to those from other secretin clinical trials, do not provide evidence to support using the hormone to treat the symptoms of autism," said Duane Alexander, M.D., director of the National Institute of Child Health and Human Development (NICHD), one of the sponsors of the study.
Interest in secretin as a possible treatment for autism, a neurodevelopmental disorder characterized by social and communication problems and repetitive behaviors and interests, arose from reports of children with autism whose symptoms improved after receiving a single dose of the hormone. Secretin is routinely given during tests to diagnose intestinal ailments, but its safety and effectiveness in treating autism were not known. Since 1999, more than a half dozen studies examined whether or not secretin could reduce symptoms in children with autism, with little evidence of benefit. Varying the doses of the hormone and giving it on more than one occasion have not proved useful in treating the disorder.
"Our study reiterates the need to perform careful studies of any new treatment--even one that appears promising--before routinely prescribing it to patients," said the study's first author, Thomas Owley, M.D., Assistant Professor of Child and Adolescent Psychiatry at the University of Chicago.
The study, conducted at sites in Illinois, California, and Utah, included 56 children with autism, ranging from age three to age 12. The children met the autistic disorder criteria for two scales used to measure the "core" symptoms of autism, the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS). The core symptoms of autism pertain to social and communication skills. The researchers confirmed the diagnosis using the DSM-IV criteria, currently the standard for diagnosing autism from the American Psychiatric Association. Children who did not meet the requirements of all three scales did not participate in the study.
Children were randomized to receive either an intravenous dose of secretin, followed by a dose of harmless saline (salt) solution four weeks later, or an intravenous dose of saline, followed by a dose of secretin four weeks later.
The children went through detailed evaluations before receiving treatment, and then every two weeks, to see if their symptoms of autism showed any change. These evaluations continued until eight weeks after treatment, to ensure that the researchers would detect any positive effect.
Using a change in the ADOS social-communication score as a primary measure, researchers found no statistically significant differences in the group when they received secretin versus when they received the placebo. Assessments of secondary measures showed no treatment effect at all between the secretin and placebo groups. The results were the same eight weeks after the treatment.
None of the five controlled clinical trials published on secretin, either in the porcine form or in the synthetic form, given at varying doses, have shown any improvement over the placebo in symptoms of autism.
Open label studies -- those in which researchers know what they are giving to the patients - comparing secretin with the saline solution, have suggested that some improvements might result when secretin is used in patients with autism. The current study was "double-blinded," meaning that neither the patients nor the researchers who treated and evaluated the patients knew when the patients received the secretin or the placebo. The purpose of studying a treatment (secretin) against a placebo (saline) in a double-blinded design is to assure objectivity in the evaluation of a person's response to a medication by eliminating any bias that might be caused by the expectations of the participants. Scientifically, a double-blinded, placebo-controlled design is considered optimal in investigations designed to determine whether a treatment is effective. This study also used a cross-over design, in which the same patients are evaluated on placebo and treatment, rather than comparing one group receiving treatment and another receiving placebo. Because of its objective nature, the study provides strong evidence that the use of secretin does not improve autistic symptoms and behaviors. However, it is not possible to say from such a relatively small study whether or not there may be a small sub-group of autistic patients who may experience some benefit from secretin.
"This multi-site study analyzed possible changes in autistic symptoms based on very well accepted measures," said Laurence Stanford, Ph.D., a program officer in NICHD's Mental Retardation and Developmental Disabilities Branch. "The study results reinforce the findings of other controlled clinical trials on secretin that, for most people with autism, the hormone is not an effective treatment."
The study was conducted as part of the Collaborative Network on the Neurobiology and Genetics of Autism, supported by the NICHD and the National Institute on Deafness and Other Communication Disorders (NIDCD), both parts of the National Institutes of Health (NIH), the biomedical research arm of the federal government. Additional support for the trial came from the National Institute of Mental Health and the National Center for Research Resources at the NIH, and from the University of California-Davis Medical Investigation of Neurodevelopmental Disorders (MIND) Institute.
The NICHD is one of the Institutes comprising the NIH, the premier biomedical research agency in the federal government. The NICHD supports and conducts research on development before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. NICHD publications, as well as information about the Institute, are available from the NICHD website, http://www.nichd.nih.gov, or from the NICHD Information Resource Center, 1-800-370-2943; E-mail NICHDInformationResourceCenter@mail.nih.gov