title: The association of growth hormone parameters with skeletal muscle phosphocreatine recovery in adult men.
abstract: BACKGROUND
  Previous studies have suggested a relationship between GH and mitochondrial function. However, little is known about the relationship of specific GH indices and in vivo measures of mitochondrial function in humans.
  
  
  OBJECTIVE
  The objective of this study was to determine the association between GH, IGF-I, and phosphocreatine (PCr) recovery, a measure of mitochondrial function, in otherwise healthy adults.
  
  
  METHODS
  Thirty-seven healthy men and women were studied at a single university medical center. Subjects underwent GH stimulation testing with GH releasing hormone-arginine and measurement of IGF-I. Mitochondrial function was determined by PCr recovery after submaximal exercise by (31)Phosphorous magnetic resonance spectroscopy. Subjects underwent assessment of lean and fat mass with use of dual energy X-ray absorptiometry.
  
  
  RESULTS
  There were no differences in PCr recovery between men and women (men 20.7±1.5 vs. women 24.8±1.4 mM/min; P > 0.05). IGF-I (r = 0.33; P = 0.04) was associated with PCr recovery in all subjects. Among men, IGF-I (r = 0.69; P = 0.003), peak stimulated GH (r = 0.52; P = 0.04), and GH area under the curve (AUC) (r = 0.53; P = 0.04) were significantly associated with PCr recovery. However, neither IGF-I, peak stimulated GH, nor GH AUC (all P > 0.05) were associated with PCr recovery in women. After adjusting for age, race, and physical activity, IGF-I remained significantly associated with PCr recovery (β = 0.10; P = 0.02) among men.
  
  
  CONCLUSIONS
  IGF-I, peak stimulated GH, and GH AUC are associated with skeletal muscle PCr recovery in men.
authors.affiliation: Program in Nutritional Metabolism and Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, LON 211, Boston, Massachusetts 02114, USA. hmakimura@partners.org
authors.forename: Hideo
authors.initials: H
authors.lastname: Makimura
authors.forename: Takara L
authors.initials: TL
authors.lastname: Stanley
authors.forename: Noelle
authors.initials: N
authors.lastname: Sun
authors.forename: Mirko I
authors.initials: MI
authors.lastname: Hrovat
authors.forename: David M
authors.initials: DM
authors.lastname: Systrom
authors.forename: Steven K
authors.initials: SK
authors.lastname: Grinspoon
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D019540:Area Under Curve; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D019382:Human Growth Hormone / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000378:metabolism; D009043:Motor Activity / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism*; D012044:Regression Analysis; D055815:Young Adult
chemical_list: D010725:Phosphocreatine; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I