title: Regulation of fuel metabolism during exercise in hypopituitarism with growth hormone-deficiency (GHD).
abstract: Growth hormone (GH) has a strong lipolytic action and its secretion is increased during exercise. Data on fuel metabolism and its hormonal regulation during prolonged exercise in patients with growth hormone deficiency (GHD) is scarce. This study aimed at evaluating the hormonal and metabolic response during aerobic exercise in GHD patients.
  
  
  
  Ten patients with confirmed GHD and 10 healthy control individuals (CI) matched for age, sex, BMI, and waist performed a spiroergometric test to determine exercise capacity (VO2max). Throughout a subsequent 120-minute exercise on an ergometer at 50% of individual VO2max free fatty acids (FFA), glucose, GH, cortisol, catecholamines and insulin were measured. Additionally substrate oxidation assessed by indirect calorimetry was determined at begin and end of exercise.
  
  
  
  Exercise capacity was lower in GHD compared to CI (VO2max 35.5±7.4 vs 41.5±5.5ml/min∗kg, p=0.05). GH area under the curve (AUC-GH), peak-GH and peak-FFA were lower in GHD patients during exercise compared to CI (AUC-GH 100±93.2 vs 908.6±623.7ng∗min/ml, p<0.001; peak-GH 1.5±1.53 vs 12.57±9.36ng/ml, p<0.001, peak-FFA 1.01±0.43 vs 1.51±0.56mmol/l, p=0.036, respectively). There were no significant differences for insulin, cortisol, catecholamines and glucose. Fat oxidation at the end of exercise was higher in CI compared to GHD patients (295.7±73.9 vs 187.82±103.8kcal/h, p=0.025).
  
  
  
  A reduced availability of FFA during a 2-hour aerobic exercise and a reduced fat oxidation at the end of exercise may contribute to the decreased exercise capacity in GHD patients. Catecholamines and cortisol do not compensate for the lack of the lipolytic action of GH in patients with GHD.
authors.affiliation: Division of Endocrinology, Diabetes and Clinical Nutrition, Inselspital, Bern University Hospital and University of Bern, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Zueger
authors.affiliation: Division of Endocrinology, Diabetes and Clinical Nutrition, Inselspital, Bern University Hospital and University of Bern, Switzerland.
authors.forename: Hannah
authors.initials: H
authors.lastname: Loher
authors.affiliation: Department of Internal Medicine, University Hospital of Basel, CH-4056 Basel, Switzerland.
authors.forename: Andrea
authors.initials: A
authors.lastname: Egger
authors.affiliation: Department of Clinical Research & Institute of Interventional, Diagnostic and Pediatric Radiology, University of Bern, Bern, Switzerland.
authors.forename: Chris
authors.initials: C
authors.lastname: Boesch
authors.affiliation: Division of Endocrinology, Diabetes and Clinical Nutrition, Inselspital, Bern University Hospital and University of Bern, Switzerland. Electronic address: emanuel.christ@insel.ch.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Christ
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D002153:Calorimetry, Indirect; D016022:Case-Control Studies; D002395:Catecholamines / Q000378:metabolism; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005260:Female; D019382:Human Growth Hormone / Q000172:deficiency / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007018:Hypopituitarism / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D057185:Sedentary Behavior
chemical_list: D001786:Blood Glucose; D002395:Catecholamines; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D019382:Human Growth Hormone; D006854:Hydrocortisone
keywords: Endurance capacity; Exercise; Fuel metabolism; Growth hormone deficiency; Lipolysis