Physiological and catecholamine response to sympathetic stimulation in turner syndrome

Abstract

Women with Turner syndrome have increased heart rate and high blood pressure (BP), and have been described as having high tolerance for emotional stress. We hypothesized that women with Turner syndrome have reduced catecholaminergic and physiological response to sympathetic stimulation, and that changes in BP and heart rate are related to their catecholamine response to sympathetic stimulation. Ten young women with Turner syndrome, age 17-34 years were the subjects of this study. Their response to sympathetic stimulation was compared to a group of 10 age-matched healthy women. After a period of 30 min resting, subjects and controls were subjected to an escalating series of sympathetic stimulation: orthostatic, cold pressor and exercise, and their plasma catecholamines and haemodynamic response were monitored and compared to resting levels. Resting heart rate was higher in Turner syndrome patients at 83 +/- 9 beats per min (bpm, mean +/- SD), as compared to controls (74 +/- 10 bpm, P < 0.05). Their supine BP was also higher at 122 +/- 9/84 +/- 6 vs. 106 +/- 11/70 +/- 9 mmHg (P < 0.02/< 0.02). The corresponding resting norepinephrine, but not epinephrine, was higher in Turner syndrome patients (2.54 +/- 1.09 nmol/l) as compared to controls (1.69 +/- 0.55 nmol/l, P < 0.02). In response to orthostatic stimulation and cold pressor test the systolic, but not the diastolic BP or heart rate, increased in Turner syndrome patients but not in the control group (P < 0.01). The change in blood catecholamine levels was comparable in both groups. Their physiological response to exercise was normal. Yet, the exercise-induced surge of norepinephrine and epinephrine in Turner syndrome patients was lower (P < 0.02). Turner syndrome is associated with dysregulation of the sympathetic nervous system (SNS), leading to tachycardia and high BP, increased resting norepinephrine levels, and a greater tolerance of the cathecholamine response to exercise.