Plasma-noradrenaline in essential hypertension.

Plasma-noradrenaline (P.N.A.) has been determined in normotensive controls and in patients with essential hypertension while resting and after postural stimulation. A linear relationship was found between age and P.N.A. in normotensives during recumbency and in the upright posture. This relationship did not occur in the hypertensives and was due to raised P.N.A. levels in many younger patients. On standing, ten out of thirty-four patients under the age of 50 years with essential hypertension had significantly greater P.N.A. than the age-matched controls. No differences were found, however, between controls and patients in the older age-group. It is proposed that stimulation of the sympathetic nervous system by postural challenge provides a means for identifying a subgroup of younger patients with essential hypertension in whom sympathetic overactivity may play an important rule.