Cerebrospinal fluid beta-endorphin and cortisol study in Rett syndrome.

An evaluation of cerebrospinal fluid and plasma beta-endorphin and cortisol levels was performed in 15 girls affected with classic Rett syndrome. There were no differences between the patient group and the control group in plasma cortisol and beta-endorphin levels. But in Rett syndrome, a significant increase in beta-endorphin was noted in the cerebrospinal fluid, with an elevation of the cerebrospinal fluid/plasma beta-endorphin ratio and a decrease in cerebrospinal fluid cortisol. A substantial overlap between patients and control group diminishes the diagnostic value of cerebrospinal fluid beta-endorphin assay in girls suspected of having Rett syndrome.