Gender influence on vasoactive hormones at rest and during a 70° head-up tilt in healthy humans

To evaluate the influence of age and gender on the neuroendocrine control of blood pressure in normal subjects, a 13-min 70degrees head-up tilt (HUT) was applied after 3 h of recumbency to 109 healthy men and women aged 23-50 yr (age group I) and 51-77 yr (age group II). We found that age and gender had a significant influence on plasma norepinephrine (PNE) concentration at baseline and in the upright position. PNE was significantly higher in older men compared with the younger men and women of both age groups, suggesting a divergent age-related activation of the sympathetic nervous system between genders at baseline as well as during a sustained orthostatic challenge. There was no significant influence of age or gender on plasma epinephrine at baseline or during HUT. Plasma renin activity was significantly higher at baseline as well as in the upright position during HUT in elderly men than in women. Age or gender had no influence on plasma vasopressin (PAVP), and, regardless of age, nonhypotensive HUT induced an extremely modest increase in PAVP. The syncopal subjects displayed a hormonal pattern associating increased PNE and a surge in plasma epinephrine and PAVP minutes before syncope during HUT. The orthostatic intolerance appears not to be a feature of healthy aging per se. In healthy subjects, both age and gender modulate markedly the cardiovascular and neuroendocnine responses to an orthostatic challenge and must be taken into consideration, particularly when catecholamine responses are studied.