Persistent tardive dyskinesia and neuroleptic effects on glucose tolerance

The relations of persistent tardive dyskinesia (TD) to glucose tolerance and family history of type 2 diabetes mellitus (FH-NIDDM) were examined in 22 schizophrenic patients. All patients underwent a standard oral glucose tolerance test (GTT) while receiving haloperidol, and 15 patients also underwent a GTT when drug free. Fasting blood glucose (FBS) was significantly higher in the TD group than in the non-TD group in the medicated condition, but not in the drug-free state. TD and non-TD groups did not differ significantly in postload glucose levels either in the drug-free or in the medicated condition. However, relative to the drug-free state, haloperidol-treated TD patients showed decreased glucose tolerance while non-TD patients showed increased glucose tolerance. Seven (32%) of the 22 patients had an FH-NIDDM. A positive FH-NIDDM was significantly associated with the presence of TD and with higher drug-free FBS. A possible role of melatonin in mediating the TD-augmenting effects of FH- NIDDM and the neuroleptic-induced decrease in glucose tolerance has been proposed.