Effect of ageing on insulin and growth hormone response to glucose and arginine in normal subjects

Glucose tolerance is considered to decrease with ageing. In order to assess the role of insulin and growth hormone (GH) in this process, insulin and GH response to arginine infusion were evaluated in 42 subjects with a normal glucose tolerance test, divided according to age into three groups (20-39, 40-59 and 60-80 years). In 6 subjects of each age group, insulin response to oral glucose was also evaluated. Blood glucose levels following the two stimuli were higher in older subjects. Insulin response tended towards higher values in older subjects. GH secretion did not vary in the three age groups. These data indicate that the deterioration of glucose tolerance is not due to diminished insulin secretion or to enhanced GH secretion. The cause of the higher glucose levels in response to arginine in the elderly remains to clarified.