Aims We examined the effects of growth hormone administration on the sympathetic nervous system in patients with idiopathic dilated cardiomyopathy. Background Growth factor therapy is emerging as a new potential option in the treatment of heart failure. Although growth hormone provides functional benefit in the short term, it is unknown whether it affects the sympathetic nervous system, which plays a role in the progression of heart failure. Methods Seven patients with idiopathic cardiomyopathy received 3 months treatment with recombinant human growth hormone (0·15–0·20 IU.kg−1.week−1). Standard medical therapy was unchanged. Myocardial norepinephrine release, both at rest and during submaximal physical exercise, plasma aldosterone, and plasma volume were measured before and after growth hormone treatment. Myocardial norepinephrine release was assessed from arterial and coronary venous plasma concentrations of unlabelled and tritiated norepinephrine and coronary plasma flow (thermodilution). Results Growth hormone induced a significant fall in myocardial norepinephrine release in response to physical exercise (from 180±64 to 99±34ng.min−1; P
