BETA-ENDORPHIN RESPONSE TO EXOGENOUS CORTICOTROPIN-RELEASING HORMONE IN OBESE WOMEN WITH DIFFERENT PATTERNS OF BODY-FAT DISTRIBUTION

Obese individuals may be characterized by higher than normal basal and stimulated beta-endorphin plasma concentrations, which suggests an increased activity of the opioid system. This study was carried out to investigate whether the regulation of beta-endorphin secretion may be different in different phenotypes of obesity. Twenty-two obese women (body mass index greater than 30 kg/m2) without other endocrine and metabolic abnormalities were investigated. A group of seven normal weight healthy women matched for age served as controls. According to the protocol, obese women included in the study had a waist-to-hip ratio higher than 0.85 (n = 9) or lower than 0.80 (n = 13). The former were defined as having abdominal type and the latter peripheral type body fat distribution. Both groups were matched for body mass index. All women randomly underwent a corticotrophin-releasing hormone test (human CRF, 1 mug/kg body weight) and a control saline study, with blood samples for beta-endorphin determination taken at regular intervals. Basal beta-endorphin levels were not significantly different between the three groups. No significant variation in the hormone levels occurred during the control study in either group. After CRF injection, however, beta-endorphin rose significantly in all women, but the hormone concentrations were significantly higher in obese women with abdominal fat distribution than in those with peripheral fat distribution and in controls. These results indicate that, among obese women, only those with the abdominal phenotype seem to have increased opioid activity.