Metallothionein and autism

Autism is a complex disorder with both genetic and environmental factors. Metal disturbances have been reported in autistic individuals. In particular, exposure to ethylmercury (EtHg) in the vaccine preservative thimerosal and exposure to methylmercury (MeHg) through fish consumption have been implicated as environmental contributors to the autism spectrum disorder (ASD) phenotype. Metallothioneins (MTs) are small sulfhydryl (-SH)-rich metal-binding proteins that have important functions in metal homeostasis and protection against metalinduced toxicity. MT1 and MT2 have a high affinity for toxic heavy metals and are induced following mercury (Hg) exposure. It has been suggested that altered or dysfunctional MTs could enhance susceptibility to Hg-induced toxicity, and that alterations in Hg metabolism may contribute to the neurodevelopmental phenotypes present in ASD. One proposed treatment of autism is to attempt to restore MT function; however, there is no evidence in the peer-reviewed literature that MT restoration is an effective treatment for autistic symptoms. To date, there is no evidence for the efficacy of MT in ameliorating MeHg-or EtHg-induced neurotoxicity. Currently, there is nothing in the literature that suggests altered MT homeostasis is a contributing factor to the development of autism.