A growing body of scientific evidence has now found decreased transsulfuration biomarkers such as glutathione, cysteine, and taurine in individuals with Autism Spectrum Disorders(ASDs).
Autism spectrum disorders are characterized by impairments in social relatedness and communication, repetitive behaviors, abnormal movement patterns, and sensory dysfunction.
Glutathione(GSH) is one of the most important substances in the human body and has a number of vital functions such as acting as a potent antioxidant and scavenger of free radicals that cause oxidative damage.
Glutathione is also extremely important for the detoxification of a number of toxins such as heavy metals(mercury) and other toxic chemicals.
Glutathione is a tripeptide molecule, which is biosynthesized in the body from the amino acids l-cysteine, l-glutamic acid, and glycine.
One study from 2009 evaluating transsulfuration metabolites in participants diagnosed with autism spectrum disorders (ASDs) found significant decreases in transsulfuration biomarkers in those with ASD’s. 
The goal of this study was to evaluate transsulfuration metabolites in participants diagnosed with autism spectrum disorders (ASDs).
Transsulfuration metabolites, including: plasma reduced glutathione (GSH), plasma oxidized glutathione (GSSG), plasma cysteine, plasma taurine, plasma sulfate, and plasma free sulfate among participants diagnosed with ASDs (n = 38) in comparison to age-matched neurotypical controls were prospectively evaluated.
Testing was conducted using Vitamin Diagnostics, Inc. (CLIA-approved).
Participants diagnosed with ASDs had significantly (P < 0.001) decreased plasma reduced GSH, plasma cysteine, plasma taurine, plasma sulfate, and plasma free sulfate relative to controls.
By contrast, participants diagnosed with ASDs had significantly (P < 0.001) increased plasma GSSG relative to controls.
The present observations are compatible with increased oxidative stress and a decreased detoxification capacity, particularly of mercury, in patients diagnosed with ASDs.
Patients diagnosed with ASDs should be routinely tested to evaluate transsulfuration metabolites, and potential treatment protocols should be evaluated to potentially correct the transsulfuration abnormalities observed.
Another study from 2006 evaluating methionine cycle-transsulfuration and androgen pathway markers in children with autistic disorders, found similar findings of decreased transsulfuration biomarkers to the above study. 
Plasma-reduced glutathione, plasma cysteine, plasma methionine, serum cystathionine, and serum homocysteine were all significantly decreased.
There now appears to be mounting scientific evidence that decreased transsulfuration biomarkers such as glutathione, taurine, cysteine and sulfate may play a potential role in the pathophysiology of Autism Spectrum Disorders(ASD’s).
The decreased transsulfuration metabolites also give an explanation to the decreased detoxification capacity, increased oxidative stress and toxic metal overload such as mercury poisoning typically seen in individuals with Autism disorders.
As the scientific research concludes, transsulfuration biomarkers such as glutathione, taurine, cysteine, and sulfate should be routinely evaluated and addressed in individuals with Autism Spectrum Disorders.
1. A Prospective Study of Transsulfuration Biomarkers in Autistic Disorders
2. A clinical and laboratory evaluation of methionine cycle-transsulfuration and androgen pathway markers in children with autistic disorders.
The information in this article has not been evaluated by the FDA and should not be used to diagnose, cure or treat any disease, implied or otherwise.