The aim of the study is to investigate changes in insulin sensitivity and ß-cell function after 24 and 48 weeks of low-dose growth hormone (GH) therapy in adult patients with severe GH deficiency using highly standardized techniques. Insulin sensitivity was estimated using euglycemic, hyperinsulinemic clamps, while insulin secretion and hepatic insulin clearance were determined by changes in insulin and C-peptide levels during hyperglycemic hyperinsulinemic clamps with consecutive intravenous (i.v.) L-arginine stimulation tests. Moreover, the researchers investigated changes in body composition, lipolysis and cardiovascular risk markers. Furthermore, in order to verify the mechanisms involved in the pathogenesis of GH-induced insulin resistance and the GH-induced improvement in insulin resistance under long term treatment, the researchers intend to establish changes in intramyocellular lipid (IMCL) in patients with GH deficiency by magnetic resonance (MR)-spectroscopy before and during GH-treatment and to correlate IMCL with insulin resistance, insulin secretion and insulin clearance. Finally, the researchers aim to justify the effect of GH on adiponectin secretion as well as on the 11-ß hydroxylase activity.