Growth Hormone (GH) Response to GH-Releasing Hormone in Children with Subnormal Integrated Concentrations of GH*

Abstract

We determined the GH responses to human GH-releasing hormone-40 (GHRH) in poorly growing children who had either normal or deficient GH secretion, as measured by pharmacological stimulation and integrated concentration of GH (IC-GH). Ten patients had both normal pharmacologically stimulated GH and IC-GH (GH-normal), 15 patients had normal pharmacologically stimulated GH but deficient IC-GH [GH neurosecretory dysfunction (GHND)], and the remaining 7 patients had both subnormal stimulated GH and IC-GH [GH deficiency (GHD)]. The mean peak plasma GH response to GHRH was 11.7 +/- 8.5 (+/- SD) ng/ml in GHD patients, significantly lower than the responses of both the GHND (49.2 +/- 39.2 ng/ml; P less than 0.0001) and GH-normal (51.8 +/- 44 ng/ml; P less than 0.0001) groups. The range of peak GH responses to GHRH in GHD patients overlapped the lower end of the range of responses in the GHND and GH-normal patients. Three GH-normal and eight GHND patients had greatly enhanced GH responses to GHRH (greater than 50 ng/ml); no GHD patients had a response over 24.2 ng/ml. There was no difference between the GH responses of male and female patients within groups to GHRH. There was a significant correlation between the log of the peak GH response to GHRH and the log of the maximal GH response to standard pharmacological stimuli (r = 0.51; P less than 0.005). Because of the variability of GH responses to GHRH encountered among the patients, the response to GHRH cannot be used as a test for identifying patients with inadequate spontaneous GH secretion. The IC-GH is the only method that can identify children with GHND.