Abnormal Vascular Reactivity in Growth Hormone Deficiency

Abstract

Background —The reason why patients with growth hormone (GH) deficiency (GHD) are at increased risk for premature cardiovascular death is still unclear. Although a variety of vascular risk factors have been identified in GHD, little is known regarding vascular reactivity and its contribution to premature arteriosclerosis. Methods and Results —We assessed vascular function in 7 childhood-onset, GH-deficient nontreated patients (age 22±3 years, body mass index [BMI] 25±1 kg/m 2 ) and 10 healthy subjects (age 24±0.4 years, BMI 22±1 kg/m 2 ) by using strain gauge plethysmography to measure forearm blood flow in response to vasodilatory agents. The increase in forearm blood flow to intrabrachial infusion of the endothelium-dependent vasodilator acetylcholine was significantly lower in GH-deficient nontreated patients than in control subjects ( P <0.05). Likewise, forearm release of nitrite and cGMP during acetylcholine stimulation was reduced in GH-deficient nontreated patients ( P <0.05 and P <0.002 versus controls). The response to the endothelium-independent vasodilator sodium nitroprusside was also markedly blunted in GH-deficient patients compared with control subjects ( P <0.005). To confirm that abnormal vascular reactivity was due to GHD, we also studied 8 patients with childhood-onset GHD (age 31±2 years, BMI 24±1 kg/m 2 ) who were receiving stable GH replacement therapy. In these patients, the response to both endothelium-dependent and -independent vasodilators, as well as forearm nitrite and cGMP, release was not different from that observed in normal subjects. Peak hyperemic response to 5-minute forearm ischemia was significantly reduced in GH-deficient nontreated patients (17.2±2.6 mL · dL −1 · min −1 , P <0.01) but not in GH-treated patients (24.8±3.3 mL · dL −1 · min −1 ) compared with normal subjects (29.5±3.2 mL · dL −1 · min −1 ). Conclusions —The data support the concept that GH plays an important role in the maintenance of a normal vascular function in humans.