title: Impaired quality of life in growth hormone-deficient adults is independent of the altered skeletal muscle oxidative metabolism found in conditions with peripheral fatigue.
abstract: BACKGROUND
  Growth hormone-deficient (GHD) adults often report impaired quality of life (QoL) - with fatigue, a key element. This deficit can improve following GH replacement. The basis of this response is unclear. Perturbations in skeletal muscle metabolism have been demonstrated in several conditions in which fatigue is a prominent symptom. We wished to define the role of skeletal muscle metabolism in the impaired QoL observed in patients with GHD.
  
  
  OBJECTIVE
  To compare in vivo skeletal muscle mitochondrial oxidative phosphorylation using phosphorus-31 magnetic resonance spectroscopy in matched untreated GHD adults, treated GHD adults and healthy volunteers.
  
  
  METHODS
  Twenty-two untreated GHD adults, 23 treated GHD adults and 20 healthy volunteers were recruited at a regional centre. All patients underwent assessment of muscle mitochondrial function (τ₁/₂ PCr) and proton handling using spectroscopy. Fasting biochemical analyses and anthropometric measurement were obtained. All patients completed the QoL-AGHDA and physical activity assessment (IPAQ) questionnaires.
  
  
  RESULTS
  Untreated and treated GHD adults complained of significantly increased fatigue and an impaired QoL (P = 0·002) when compared to healthy controls. There was no difference in maximal mitochondrial function (P = 0·53) nor pH recovery (P = 0·38) of skeletal muscle between the three groups. Untreated GHD patients had significantly lower IGF-1 than both treated GHD and healthy volunteers (P < 0·001), but there was no association between τ₁/₂ PCr and serum IGF-1 (r = -0·13, P = 0·32).
  
  
  CONCLUSIONS
  The impaired QoL seen in GHD adults is not associated with the skeletal muscle spectroscopic 'footprint' of altered mitochondrial oxidative function, anaerobic glycolysis or proton clearance that are a feature of several conditions in which fatigue is a prominent feature. These data suggest that the pathophysiology of fatigue and impaired QoL in GHD may have a significant central rather than peripheral (skeletal muscle) component.
authors.affiliation: Department of Paediatric Endocrinology, Great North Children's Hospital, Newcastle-upon-Tyne, UK; Institute of Genetic Medicine, Newcastle University, Newcastle-upon-Tyne, UK.
authors.forename: Akash
authors.initials: A
authors.lastname: Sinha
authors.forename: Kieren G
authors.initials: KG
authors.lastname: Hollingsworth
authors.forename: Steve
authors.initials: S
authors.lastname: Ball
authors.forename: Tim
authors.initials: T
authors.lastname: Cheetham
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D005221:Fatigue / Q000097:blood* / Q000378:metabolism*; D005260:Female; D013006:Growth Hormone / Q000097:blood* / Q000172:deficiency*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D011788:Quality of Life; D055815:Young Adult
chemical_list: D013006:Growth Hormone