Oxytocin and autistic disorder: Alterations in peptide forms

Background: Oxytocin (OT) is synthesized as a prohormone that is sequential ly processed to peptides. These peptides are the bioactive amidated form (O T) and the C-terminal extended peptides, OT-Gly, OT-Gly-Lys and OT-Gly-Lys- Arg, which are designated together as OT-X. As an extension of our previous study finding decreased plasma OT in autism, studies were conducted to det ermine whether there were changes in OT peptide forms in autistic children. Methods: Twenty eight male subjects (97 +/- 20 months; range, 70 -139 month s), diagnosed with DSM-IV autistic disorder through observation and semi-st ructured interview, were compared with 31 age-matched nonpsychiatric contro l subjects (106 +/- 22 months; range, 74-140 months). Using OT antisera wit h different specificity for the peptide forms, we measured plasma OT and OT -X in each group. Results: T tests showed that there was a decrease in plasma OT (t = 4.4, p < .0001), an increase in OT-X (t = 2.3, p < .03) and an increase in the rat io of OT-X/OT (t = 4.5, p < .0001) in the autistic sample, compared with co ntrol subjects. Conclusions: The results suggest that children with autistic disorder show alterations in the endocrine OT system. Deficits in OT peptide processing i n children with autism may be important in the development of this syndrome . (C) 2001 Society of Biological Psychiatry.