Intestinal hormone secretin should not be used to treat autism

The intestinal hormone secretin, considered by some to be a promising drug in the treatment of autism, does not improve the symptoms and should not be used to treat the disorder, according to a new review of studies.

After analyzing data from 14 high-quality studies involving 618 patients with autism disorders, Dr. Katrina Williams of the Children's Hospital at Westmeade, Sydney, Australia, and colleagues found no evidence that doses of intravenous secretin improve the social, behavioral or communication problems associated with autism.

Secretin "should not currently be recommended or administered as a treatment for autism," the reviewers conclude. There were no serious side effects reported in any of the studies, but "more adverse events are likely to be reported if secretin is made widely available," Williams says.

The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

In 1998, a series of small studies by Karoly Horvath and others at the University of Maryland School of Medicine hinted that secretin might be useful in treating autism. In the studies, children with symptoms of autism and gastrointestinal disorders were given pig secretin as part of an endoscopic procedure to examine their digestive functioning. Horvath and colleagues reported, to their surprise, that some autism symptoms seemed to improve in children who received the hormone.

"Since then, the use of secretin has become widespread and it is currently being dispensed in many different forms and in countries where it is not licensed," Williams says.

Although several controlled studies have since found little evidence that the hormone can improve the key symptoms of the disorder, some people with autistic disorders and their families still hold high hopes for secretin. Stories of how the hormone has transformed some patients' lives and purchasing information for secretin can be found across dozens of Internet sites.

"The many needs of these individuals trigger hope for a cure," Williams says. "As a result, therapies like secretin have become widely used after limited reports of success."

In the 14 studies reviewed by Williams and her colleagues, patients were diagnosed with classic autism or similar disorder such as Asperger syndrome. The patients, ranging in age from 3 to 15 years old, were given either synthetic human secretin or pig secretin or a saline placebo intravenously.

The Cochrane reviewers found no evidence that secretin improved the core features of autism, such as problems with social interaction, impaired speaking skills and repetitive behaviors.

Despite the findings, parents of autistic children may not be willing to give up their faith in secretin. Williams and colleagues cite a 1999 study in which 63 percent of parents whose children received the hormone treatment remained interested in secretin, even after the treatment failed to produce significant improvements.

Parents and patients are intensely interested in autism treatments, but most suggested therapies for autism disorders are "invasive, time consuming and expensive, and there is little known about their potential to do harm," Williams says.

In the face of such daunting options, parents often turn to alternative or complementary medicine for their children, according to Dr. Susan Levy of the Children's Hospital of Philadelphia. At Children' Hospital, one in three children recently diagnosed with autism received alternative medical treatments, a 2004 survey by Levy and others found.

Autism disorders usually appear during the first three years of life, and may be four times more likely to occur in boys compared to girls. The prevalence of autism is disputed. A 2003 study estimated that 40 out of every 10,000 children in the United States might have an autistic disorder, but other studies estimate the prevalence as less than one out of every 10,000 children.

In recent months, some politicians and patients have also suggested that a mercury compound called thimerosal, formerly used as a preservative in vaccines, may be one of the culprits behind autism. Although the purported connection has been well publicized, the Institute of Medicine concluded earlier this year that there is no evidence of a link between vaccines and autism.

Autistic disorders are probably caused by a combination of genetic, environmental and brain development factors, Williams says.