The place of intravenous GHRH 1-40 studies in the therapy of growth hormone-deficient children with GHRH.

We studied GH responses to i.v. GH releasing hormone (GHRH) (1 microgram/kg) before and during the treatment of 11 GH deficient children with s.c. nocturnal pulsatile GHRH 1-40; seven for 9 months and four for 6 months. Each subject demonstrated GH stimulation at each i.v. study. There was a wide variation of response between subjects and in each subject on different occasions. Significant growth acceleration following s.c. GHRH was demonstrated in eight of 11 patients (73%). The sensitivity or true positive rate of the index GHRH study to predict a clinical response to s.c. treatment, regardless of the GH response achieved, was also 73%. When an index GH 'cut-off' response of less than 10 mU/l was employed, the probability of an increase in growth rate to s.c. GHRH fell to 0.50 (sensitivity 80%). The GHRH study was unhelpful, and in fact misleading, when assessed as a method of monitoring clinical progress and the outcome of pulsatile s.c. GHRH treatment. The growth response of a child to s.c. GHRH therapy is of far greater importance than the GH response following an i.v. bolus of GHRH. The index study gave no useful indication of either the potential GH pituitary reserve or which subjects would respond to treatment. Pretreatment and repeated GHRH studies are of limited value and should be interpreted with caution.