Urinary peptides in Rett syndrome.

Researchers collected morning urine from girls with Rett syndrome. They compared peptide levels to healthy girls of the same age. The lab measured opioid-like fragments that come from digested food proteins.

Girls with Rett syndrome had much higher peptide levels. The amounts matched those seen in autism studies. Higher peptide scores tracked with more severe Rett symptoms.

Attwood et al. (1988) saw no peptide rise in young autistic men. The clash clears up when you note the groups: young adult males versus little girls with Rett. Same lab test, different populations.

Öztürk et al. (2026) pooled 17 trials on gluten-free, casein-free diets. They found weak proof that cutting these proteins lowers peptides and helps autism traits. The Rett data hint the diet might also aid girls with high peptide scores.

Lussu et al. (2017) used a fancier urine test in autistic children. They also spotted unique chemical fingerprints. Both papers back the idea that urine can flag gut–brain problems, even if the exact molecules differ.

You now have a quick, non-invasive screen for Rett syndrome severity. If a girl’s peptide level is high, track it monthly. Share the number with her doctor and dietitian. Consider a brief gluten-free, casein-free trial while you record behavior and sleep data. One clean morning sample can guide team decisions without extra blood draws.