Response of plasma insulin to small doses of tolbutamide in obesity and acromegaly
Pelkonen, R.; Taskinen, M.R.; Nikkilä, E.A.
International Journal of Obesity 1(4): 315-324
1977
ISSN/ISBN: 0307-0565 PMID: 617112 Document Number: 119718
The early response of plasma insulin (IRI) to successive intravenous doses of 50, 100 and 200 mg tolbutamide was studied in nondiabetic obese subjects, in acromegalic patients and in healthy controls. The smallest dose increased plasma IRI within 2 min in all subjects. The insulin response was correlated with basal IRI in controls and in obese subjects but not in acromegalic patients. At each tolbutamide dose the mean IRI response of obese subjects was about 3 times that in controls. In acromegalic subjects an increased response was observed only after 200 mg tolbutamide. The results suggest that in obesity the stimulus-secretion coupling of insulin output is normal but the number of secretory units is increased. In acromegaly the insulin release pattern is compatible with an increased number of secretory units which, however, are relatively insensitive to tolbutamide, probably due to increased serum somatotropin.