Ghrelin is a relatively 'new' hormone that is produced in the stomach and to a lesser extend in the hypothalamus of the brain. The actions of ghrelin are diverse and includes stimulation of the appetite center of the brain and the release of growth hormone. We have for the first time shown that ghrelin also stimulates the metabolism of fatty acids and induces insulin resistance in skeletal muscle. These effects have we confirmed in growth hormone deficient subjects on a stabile substitution treatment with growth hormone and hydrocortisone. With these subjects we can investigate the effects of ghrelin that are independent of growth hormone. The present study is a continuation of these findings, as we wish to investigate whether the insulin resistance effect of ghrelin is dependent of the concomitant metabolism of fatty acids. This is possible by administration of the niacin acid antagonist Acipimox, that blocks the fatty acid metabolism reversibly. We have applied this experimental principle in other settings with success.