Does Orthostatic Stress Influence the Neuroendocrine Response to Subsequent Hypoglycemia in Humans?

doi:10.1196/annals.1296.071

Neuroendocrine response to stress stimuli is influenced by previousstimuli of different nature. The aim of the study was to testwhether antecedent orthostatic stress may affect the neuroendocrineresponse to subsequent hypoglycemia. A group of 12 (6 men, 6women) nonobese, healthy volunteers aged 19 to 27 y (mean 24± 0.8) participated in the study in two sessions: controlledinsulin-induced hypoglycemia to 2.7 mmol/L for 15 min eitherwith or without antecedent orthostatic stress (30 min of 60°head-up tilt before insulin administration). Orthostatic stresscaused a significant decrease in plasma volume (–9.6%;P < 0.001) and a significant increase in plasma renin activity,aldosterone, norepinephrine (P < 0.01), and adrenocorticotropichormone (ACTH) concentrations (P < 0.05) in all subjects.Growth hormone response to hypoglycemia was diminished in women(P < 0.01). The epinephrine response to hypoglycemia wasdiminished in women in comparison to men (P < 0.001), butwas unaffected by antecedent orthostatic stress. Hypoglycemiafailed to induce the ACTH release after its elevation duringorthostatic stress. ACTH response to moderate hypoglycemia withoutprevious orthostatic stress was evident only in men in comparisonto women (P < 0.05). We conclude that the epinephrine, growthhormone, and ACTH responses to hypoglycemia were diminishedin women. Except ACTH, the neuroendocrine response to mild hypoglycemiawas not affected by previous orthostatic stress in healthy subjects.In the case of ACTH, the first stress stimulus is consequentialfor the subsequent response of this hormone, probably due toshort-loop negative feedback effects.