Effects of long-term L-dopa therapy on carbohydrate metabolism in patients with Parkinson's disease.
Carbohydrate metabolism and insulin secretion were investigated in 26 patients with Parkinson's disease before and during L-dopa treatment. Oral glucose tolerance tests were performed on 13 patients treated with L-dopa alone and on 7 patients treated with L-dopa combined with Carbidopa. Intravenous glucose tolerance tests were performed on additional 6 patients treated with L-dopa alone. Results indicate that chronic L-dopa administration does not modify glucose metabolism. It was observed only a significant decrease of insulin secretion after oral glucose in the early phase (15th day) of treatment with L-dopa alone. This temporary effect may be related to the peripheral conversion of L-dopa to dopamine since insulin secretion during combined therapy was normal. The mechanism by which L-dopa transiently inhibits insulin release is not clear. Perhaps the oral administration of L-dopa alone causes an alteration in some gastrointestinal functions which are involved in the handling of oral glucose.
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis; D050260:Carbohydrate Metabolism; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007980:Levodopa / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000188:drug therapy* / Q000378:metabolism; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin; D007980:Levodopa