Insulin and growth hormone secretion stimulated by intravenous administration of arginine in the low insulin responders (prediabetes?). 
Twelve apparently healthy subjects who showed a low insulin response to glucose were selected from two different age groups, 6 from youngers aged 19 to 22 and 6 from olders above 65 years old, and responses of insulin and growth hormone secretion to an intravenous administration of arginine were investigated.  Incidence of low insulin responders, who showed the peak value of plasma insulin during GTT below 45 muU/ml, was 9% among the young subjects and 24% among the old ones.  Insulin secretion stimulated by arginine in 6 young low responders was not different from that in the control group matched with regard to age and body weight, and the values of growth hormone during arginine infusion were higher than those of the control group.  In the old low insulin responders, insulin secretion stimulated by arginine was significantly lower than that in the control group, but the growth hormone secretion was not different from that in control.  The present study showed that insulin and growth hormone secretion stimulated by arginine in young low-insulin-responders were different from those in the old ones.  The low insulin responders are discussed in regard to prediabetes.