Plasma cortisol and β-endorphin immunoreactivity in human obesity

The relationship of the endogenous opioid system and the hypothalamic-pituitary-adrenal axis to obesity was studied. Morning levels of plasma cortisol and β-endorphin immunoreactivity in obese patients before diet treatment were found to be no different from those in matched family members of normal weight. In 32 untreated obese patients, no relationship between weight or body mass index (a measurement of obesity) and plasma levels of β-endorphin immunoreactivity or cortisol was found. However, plasma cortisol levels were significantly correlated with obese patient ratings on the depression subscale of the General Health Questionnaire. Dexamethasone administration failed to suppress plasma β-endorphin levels in untreated obese patients, but this finding has been reported in normal subjects in whom a similar assay methodology was used; it suppressed plasma cortisol levels in 29 of 32. The three patients resistant to suppression also suffered from benign essential hypertension. Plasma β-endorphin immunoreactivity was unchanged, but cortisol levels significantly decreased as weight was lost on a 400-calcorie/day modified protein fast. Patients who failed to complete the 6-month diet program had significantly increased plasma β-endorphin levels compared to those who successfully completed the program.