GLUCAGON: AN EFFECTOR OF ACTH, CORTISOL (F), AND GROWTH HORMONE RELEASE

Abstract

Glucagon (G), an accepted provocative stimulus for hGH release, would have greater usefulness if shown to effect the release of other trophic hormones. hGH response to G was studied in 10 children, ages 6-14 yrs, with simultaneous evaluation of ACTH and F responses.

Beginning at 0800 hrs, specimens were obtained at 30' Intervals for hGH, ACTH, and F, which were measured by RIA, and for blood glucose (autoanalyzer), between −30 and +180' after a img IM dose of G.

hGH responses were normal in 8/10 patients (> 10 ng/ml). In these 8, two types of ACTH-F response were noted; in 5 patients with a fasting F(F_O) of < 10 μg/dl, ACTH increased 4.5-fold (Δ ACTH 40-393 pg/ml), and F 5.6-fold (Δ F 15-27.3); the mean ACTH peak occurred at 150' and mean F peak at 180'. In two patients with an F_o > 10/ μg/dl, ACTH increased only two-fold (A ACTH 6 and 265 pg/ml), and F 1.5-fold (Δ 9.8 and 23.0 μg/dl). The ACTH and F peaks occurred as in the first group. One patient showed no change in F (range 19.5-23.0 μg/dl) and a 60% decrease in ACTH between 120' and 150'.

Two of the ten children had hGH and TSH deficiency. One had an F_o of < 0.5 μg/dl and a rise in F to only 7.2; his ACTH increased from 10 to 38.0 pg/ml. The second patient showed an increase in F from 10.5-23.5 μg/dl; her ACTH increased from 37-50 μg/ml.

The pattern of the glucose response was similar in all groups, depicting the classic blphasic curve, with a hyperglycemic phase followed by a gradual decline in concentration. Nausea and Abdominal discomfort were present in only one patient.

This study shows glucagon to be a reliable and safe provocative stimulus, not only for hGH release, but also for the assessment of the pituitary-adrenal axis. Studies, in progress, should help to elucidate its mechanism of action.

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