title: Skeletal muscle mass in acromegaly assessed by magnetic resonance imaging and dual-photon x-ray absorptiometry.
abstract: BACKGROUND
  GH and IGF-I are nitrogen retaining and anabolic, but the impact of long-term exposure to supraphysiological GH and IGF-I, either from endogenous overproduction in acromegaly or exogenous sources, on skeletal muscle (SM) mass is not clear.
  
  
  OBJECTIVE
  The objectives of the study were to assess SM mass by whole-body magnetic resonance imaging (MRI) in acromegaly and test the hypothesis that dual-energy x-ray absorptiometry (DXA) lean tissue mass-derived estimates of SM accurately estimate true SM mass.
  
  
  METHODS
  The design was a cross-sectional study in 27 acromegaly patients compared with predicted models developed in 315 nonacromegaly subjects and to matched controls.
  
  
  METHODS
  Mass of SM from whole-body MRI and lean tissue from DXA were measured.
  
  
  RESULTS
  SM mass did not differ from predicted or control values in active acromegaly: 31.75 +/- 8.6 kg (acromegaly) vs. 33.06 +/- 8.9 kg (predicted); SM was 95.6 +/- 12.8% of predicted (range 66.7-122%) (P = 0.088). Lean tissue mass (DXA) was higher in acromegaly than controls: 65.91 +/- 15.2 vs. 58.73 +/- 13.5 kg (P < 0.0001). The difference between lean tissue mass (DXA) and SM in acromegaly patients was higher than that in controls (P < 0.0001) consistent with an enlarged non-SM lean compartment in acromegaly. SM mass predicted by DXA correlated highly with SM mass by MRI (r = 0.97, P < 0.0001). SM (MRI) to SM (DXA predicted) ratio was 1.018 (range 0.896-1.159), indicating high agreement of these measures of SM.
  
  
  CONCLUSIONS
  SM mass in active acromegaly patients did not differ from predicted values. SM mass estimated from DXA agreed highly with SM by MRI, supporting the validity of the DXA model in assessing SM in acromegaly and other disorders of GH/IGF-I secretion.
authors.affiliation: Department of Medicine, Columbia University College of Physicians and Surgeons, 630 West 168th Street, New York, NY 10032, USA. puf1@columbia.edu
authors.forename: Pamela U
authors.initials: PU
authors.lastname: Freda
authors.forename: Wei
authors.initials: W
authors.lastname: Shen
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Reyes-Vidal
authors.forename: Eliza B
authors.initials: EB
authors.lastname: Geer
authors.forename: Fernando
authors.initials: F
authors.lastname: Arias-Mendoza
authors.forename: Dympna
authors.initials: D
authors.lastname: Gallagher
authors.forename: Steven B
authors.initials: SB
authors.lastname: Heymsfield
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000172:Acromegaly / Q000473:pathology*; D000328:Adult; D001823:Body Composition; D003430:Cross-Sectional Studies; D005260:Female; D019382:Human Growth Hormone / Q000172:deficiency; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology*
chemical_list: D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I