The Effect of Clozapine on Factors Controlling Glucose Homeostasis

Background: This prospective study examines the effect of clozapine on factors determining glucose homeostasis.

Method: The sample consisted of all patients meeting DSM-IV criteria for schizophrenia who commenced clozapine treatment within the South London and Maudsley hospitals during 1 year (2000-2001). Growth hormone (GH), insulin-like growth factor-1 (IGF-1), and IGF binding protein-1 (IGFBP-1) were measured in 19 patients (10 female; mean age = 31.1 years [SD = 5.8]; 9 black British/African, 10 white British) before and after a mean of 2.5 (SD = 0.9) months of clozapine treatment.

Results: Baseline IGFBP-1 was low. IGFBP-1, GH, and IGF-1 were not significantly changed by clozapine treatment.

Conclusions: Clozapine does not alter GH, IGF-1, or IGFBP-1 within 3 months of commencing treatment, indicating that alteration in glucose tolerance associated with clozapine treatment involves other mechanisms yet to be elucidated. Baseline abnormalities in IGFBP-1 indicate a preexisting susceptibility to glucoregulatory dysfunction.