Endocrine Abstracts

Background

Patients with Growth Hormone Deficiency (GHD) are known to have an excess risk of vascular disease. Previous work has shown an increase in their arterial stiffness. The effect of GH on blood pressure is still unclear.

Materials and Methods

16 patients with GHD (6 males) and no history of existing vascular disease or hypertension, between the ages of 18 and 65 were recruited (mean 45.4 plus/minus 3.5 years). An insulin tolerance test was carried out and peak GH was less than 3 micrograms per litre. An open crossover design was used with patients receiving GH or no therapy for 6 months each. Other pituitary replacement was unchanged for 1 year prior to and during the study. Pulse Wave Velocity (Complior, Colson) and 24 hour ambulatory blood pressure monitoring (Spacelabs Medical) were measured at baseline, 6 and 12 months. The protocol was approved by the Western Infirmary Ethical Committee.

Results

6 months of GH therapy achieved target increase in insulin-like growth factor 1 (67.7 plus/minus 7.2 to 166.7 plus/minus 16.2 micrograms per litre, p less than 0.001). A significant reduction in mean Pulse Wave Velocity from 8.1 plus/minus 0.4 to 6.7 plus/minus 0.5 metres per second (95% C.I. 0.27, 2.65, p=0.02) was observed during GH therapy. 24 hour Mean Arterial Pressure (MAP) also fell from 91.9 plus/minus 1.6 to 88.4 plus/minus 1.6 millimetres of mercury (95% C.I. 0.11, 6.77, p=0.04) and Diastolic BP (DBP) from 76.5 plus/minus 1.3 to 73.3 plus/minus 1.4 millimetres of mercury (95% C.I. 0.33, 6.17, p=0.03). There was no significant change in systolic BP, the circadian rhythm of BP or heart rate (HR).

Discussion

GH therapy reduces arterial stiffness in patients with GHD and leads to a reduction in MAP and DBP without affecting HR. These effects of GH may be mediated through an increase in the availability of endothelial derived vasorelaxant agents. In the long-term this effect may be important in reducing vascular risk.