Decreased levels of ghrelin, cortisol, and fasting blood sugar, but not n-octanoylated ghrelin, in Japanese schizophrenic inpatients treated with olanzapine

The mechanism by which chronic administration of olanzapine induces a marked weight gain in patients with schizophrenia remains unknown. We examined the influence of long-term treatment with olanzapine on plasma levels of hormones regulating food intake and energy homeostasis in schizophrenia. In this study, olanzapine was administered to 28 Japanese inpatients for 16 weeks after switching from typical antipsychotic drugs or risperidone. At endpoint, no significant changes in body weight or body mass index were found. There was a significant decrease in the plasma levels of ghrelin without any accompanying change in active, n-octanoylated ghrelin. Serum levels of leptin tended to be increased and a significant reduction in plasma cortisol levels was found. In addition, the levels of fasting blood sugar as well as free fatty acid were significantly decreased. Furthermore, we did not confirm any marked weight gain induced by chronic administration of olanzapine as previously reported. The reason for this discrepancy may be due to differences in subjects and treatment settings. Based on these findings, it is unlikely that the decrease in plasma ghrelin levels by chronic administration of olanzapine affects weight gain. Further studies examining the effect of chronic olanzapine administration on weight and energy homeostasis in inpatients are required.