Endocrine Abstracts

Introduction: Opioid system activity was found disturbed in several reward circuit areas in restrictive anorexia nervosa (AN) patients but also surprisingly at the pituitary level. However, the potential role of this specific abnormality of pituitary in AN physiopathology remains unclear or unknown.

Objectives: The first aim was to find the exact pituitary location (posterior and/or anterior) of this disturbed opioid activity and then to study the link between this disturbed opioid activity and pituitary hormone activity.

Methods: In vivo [¹¹ C] diprenorphin cerebral non-displaceable binding potential (BP_ND) was assessed by PET imaging. Volumes and intensities were also extracted from MRI scans and processed for each pituitary region and compared in three groups of young women: 12 undernourished (AN), 11 recovered AN patients (ANrec), and 12 Controls (C). A lower BP_ND may account for an increased opioid tone and vice versa. Plasma hormones from anterior pituitary and neurohypophysis (NH) twelve points circadian profile including copeptin and oxytocin, endogenous opioids levels and psychological scores eating-related, were evaluated in these subjects as well as in 13 bulimic (BN) patients.

Results: [¹¹ C] diprenorphin pituitary binding was found to be fully localized in NH. Only AN patients’ NH present lower [¹¹ C] diprenorphin BP_ND than Controls, interpreted as a higher opioid tone. AN had lower anterior pituitary volume than controls and ANrec while ANrec still had a smaller anterior pituitary volume than controls. Concerning posterior pituitary volume, only AN had significant lower volume than controls. NH [¹¹ C] diprenorphin BP_ND correlated directly with the anterior pituitary volume. Both AN and ANrec show lower copeptin/24h than in Controls but no difference in oxytocin. BN patients showed an increase in copeptin and a decrease in oxytocin levels compared to Control group. In AN patients copeptin inversely correlate with Restrained Eating while oxytocin correlate with the External Eating score. NH [¹¹ C] diprenorphin BP_ND correlated among others things with leptin, BMI, pituitary BP, hypothalamus BP, Amygdal IBP, but not with copeptin or oxytocin.

Conclusion: The disruption of opioid activity observed in the previous study appears to be mainly localized in the neurohypophysis. Neurohypopysis opioid tone in AN seem not to impact the vasopressin or oxytocin release but still may interfere in gonadal axis regulation. Copeptin seems to be a good indicator of hydration state and may be a good tool to detect hidden restrictive or purging behaviors. Specific correlations with the psychological characteristics of anorexia nervosa still suggest a pathophysiological involvement.