Tardive Dyskinesia and Glucose Metabolism

To the Editor.— We read with interest the letter by Mukherjee et al1in which an increased incidence of a high fasting blood sugar (FBS) level was found among subjects with tardive dyskinesia (TD). We would like to add that an impaired FBS level has been observed in other exprapyramidal disorders in which dopamine has been shown to play a pathogenetic role, namely, chorea2and Parkinson's disease.3 As early as 1960, Gates and Hyman4reported on the efficacy of oral tolbutamide in diabetic subjects with PD, and in 1961 Barbeau5found decreased glucose tolerance in 50% of subjects with PD. Van Woert and Mueller6found increased FBS and decreased plasma insulin levels in 24 subjects with PD. These findings were attributed to a decreased release of pancreatic insulin in PD. Indeed, dopamine has been shown to stimulate insulin secretion (a βadrenergic—mediated mechanism)7and