Growth hormone replacement therapy in adults with growth hormone deficiency improves vascular reactivity

Patients with adult growth hormone (GH) deficiency are thought to be of increased risk of cardiovascular disease. Impaired vascular reactivity to endothelium derived nitric oxid (NO) is an early event in the development of atherosclerosis. In order to detect a possible effect of GH on vascular endothelium we examined forearm vasodilator responses in 8 patients with adult GH-deficiency before and after 3 months GH replacement therapy.

Forearm blood flow studies were performed using venous occlusion plethysmography. Blood flow was measured at baseline and during intra-arterial infusions of 3 cumulative doses (7.5, 15 and 30 microg/minutes) of acetylcholine chloride and of sodium nitroprusside (1, 3 and 10 microg/minutes). Fasting blood samples were collected for measurement of lipid profile, Haemoglobin A1C (HbA1C), glucose, IGF-I and insulin.

GH replacement therapy significantly increased IGF-I concentrations and tended to increase fasting insulin concentrations (IGF-I: 72.7 +/- 12.4 vs. 130.8 +/- 18.5 microg/l, P < 0.001; fasting insulin: 14.3 +/- 3.4 vs. 32.9 +/- 18.6, mU/l, P = 0.06). Fasting lipid profile, glucose and HbA1C did not significantly change. Blood flow responses to acetylcholine were significantly greater after GH replacement therapy (10.3 +/- 1.0 vs. 17.6 +/- 2.5 ml/minutes/100 ml for the highest dose, P < 0.03). There was a strong tendency to increased blood flow response to nitroprusside after GH therapy (10.7 +/- 1.2 vs. 17.5 +/- 1.7 ml/minutes/100 ml for the highest dose, P = 0.06).

These findings suggest that GH replacement therapy may have a beneficial effect on endothelium function which is independent of quantitative changes in fasting lipid profile.