This study aims at investigating the effect of growth hormone on lipid-content of muscle and liver as well as visceral fat mass in relation to insulin sensitivity.

In addition, hormonal regulation and free fatty availability is assessed during a physical exercise at 50-60% VO2max.

Finally, the value of physical exercise in diagnosing growth hormone deficiency is investigated.

Hypothesis: 1) Lipid content of muscle and liver change with physical exercise and exercise capacity and free fatty availability will influence these changes. 2)Growth hormone replacement therapy will predominantly reduce visceral fat mass and increase free fatty availability.

3)Free fatty availability during exercise will be reduced in growth hormone deficient patients 4)Physical exercise may be an alternative way to diagnose growth hormone deficiency

Using the two-step hyperinsulinaemic-euglycaemic clamp technique hepatic and peripheral insulin sensitivity is assessed.

Lipid depots (skeletal muscle and liver) are measured by MR-spectroscopy, visceral fat mass by MR-imaging.

Exercise capacity ist measured on a treadmill. Counterregulatory hormones, glucose and free fatty acids are measured during a 2h physical exercise at 50-60 VO2max Identical investigations are performed in adult growth hormone (GH) deficient patients before and after six months GH replacement therapy, in sedentary matched control subjects and in endurance trained athletes.

Inclusion Criteria:

• Male and female patients with proven GH-deficiency defined as a peak GH of less than 3mU/l during an insulin provocation test with nadir plasma glucose less than 2.2 mmol/l and additionally, stable conventional replacement therapy including corticoids, thyroxin and gonadal hormones as needed.
• Ability to perform an exercise test on a treadmill or a walking band.
• Willingness to participate in the study and to give written informed consent.

Exclusion Criteria:

Active neoplasia

• Severe cardiovascular disease (unstable coronary heart disease, heart failure NYHA III-IV)
• Type 2 Diabetes mellitus
• Haemophilia or other coagulation disorder
• Inability to exercise
• Contraindications to exposure to a 3-T magnetic field (Pace-Makers, osteosynthetic material)
• Pregnant women
• Women in childbearing age unless on a continuous contraceptive therapy or surgically sterilised.
• Abnormal liver or renal function (Creatinine >130mmol/L, normal reference 45-93mmol/L; ASAT and ALAT > 3 times the upper reference limit).
• Major depression, psychosis and other severe personality disorders
• Excessive alcohol consumption (>60g/d) or drug-abuse
• Refusal to give written consent
• Patients, who are not suitable for the study according to the study physician