A single growth hormone determination 30 minutes after the administration of the GHRH plus GHRP-6 test is sufficient for the diagnosis of somatotrope dysfunction in patients who have suffered traumatic brain injury

As hypopituitarism is frequent in patients who have suffered a traumatic brain injury (TBI) a hormonal check-up is necessary. However, the prevalence of TBI is so large that the number of potential candidates to be tested is difficult to manage, in particular for GH deficiency diagnosis that requires cumbersome and expensive dynamic tests. GHRH plus GH-releasing hexapeptide (GHRP-6) is a safe and effective test capable of segregating normal subjects from GH deficient patients. As the GHRH+GHRP-6 test induces GH peaks consistently in the first 30 min, the working hypothesis assessed in this study was whether a single determination of GH 30 min after stimulus could provide the same biochemical classification as the whole secretory curve. A total of 83 subjects who suffered TBI at least one year before the study were administered GHRH 1 μg/kg iv plus GHRP-6 1 μg/kg iv at 0 min, and blood samples were obtained at regular intervals. GH was determined in all samples. An excellent correlation was observed between GH values at 30 min and GH peaks (r=0.972, p<0.0001 ). When comparing the 30-min GH values against the peaks, the biochemical classification changed only in 5 out of 83 subjects from normal GH secretion to uncertain. Conclusions: The GHRH+GHRP-6 test is convenient, safe and in patients with TBI can be reduced to a single fixed GH determination 30 min after stimulus without losing diagnostic power.