Growth hormone responses to oral glucose loading measured by highly sensitive enzyme immunoassay in normal subjects and patients with glucose intolerance and acromegaly.

Plasma GH levels were determined during a 75-g oral glucose tolerance test using a highly sensitive enzyme immunoassay. Most normal subjects and patients with varying degrees of impaired glucose tolerance showed a decrease in plasma GH levels during the first 60 min. A GH rise within 60 min was observed in 3 of 37 normal subjects. The incidence of the GH rise (8%) was significantly lower than that (40%) in control experiments after water loading. The median minimum GH levels were 0.15 and 0.14 micrograms/L after glucose and water loading, respectively. Plasma GH responses to glucose ingestion were not different between normal subjects and patients with glucose intolerance. After surgery, 12 of 16 patients with acromegaly showed low basal GH levels (less than 5.0 micrograms/L). Six of the 12 patients showed normal GH responses to glucose loading (median minimum GH level, 0.21 micrograms/L) and normal plasma insulin-like growth factor-I levels. Plasma GH levels were not suppressed below 1.0 micrograms/L in the remaining 6 acromegalic patients. Determination of plasma GH levels after glucose loading by the highly sensitive enzyme immunoassay is useful for evaluating the effect of surgical treatment of acromegaly.