This study will investigate the non-growth-hormone-dependent metabolic effects of the hormone Ghrelin in growth hormone deficient subjects by examining the insulin tolerance as well as signal proteins in fat and muscle biopsies.

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.

Knowledge of the effects of ghrelin in general can in shot-sight as well as in long-sight have great importance for the understanding of growth disorders from overweight and type 2 diabetes to malnutrition and eating disorders.

Inclusion Criteria:

• males with hypopituitarism in regard to growth hormone and ACTH in stabile treatment regime
• age 18-65
• BMI 20-35

Exclusion Criteria:

• abuse of alcohol
• malign disease
• medication other than that expected for hypopituitarism
• known disease other than hypopituitarism
• participation in isotope investigations the last 6 months