Absence of response to hypothalamic stimulation test in brain death

Immunoreactive corticotropin-releasing hormone (CRH) and growth hormone-releasing hormone (GHRH) are present in the plasma of the brain dead patients. These hypothalamic hormones may reflect some residual brain function after brain death. To examine the hypothalamic function, insulin-induced hypoglycemia and arginine infusion were performed in brain dead patients. Plasma CRH and GHRH were present initially, but levels did not increase significantly for 120 minutes after insulin injection. GH, adrenocorticotropic hormone, and cortisol levels did not increase either. Arginine load did not induce GH. These results suggest that hypothalamic hormones in the plasma after whole brain death do not reflect hypothalamic functions. The hormones may originate from extrahypothalamic sources such as the pancreas or adrenal gland.