title: PSA and body composition by dual X-ray absorptiometry (DXA) in NHANES.
abstract: BACKGROUND
  Obese men are at higher risk for advanced prostate cancer and have a poorer prognosis following treatment. Several studies also report that obese men have lower blood PSA levels, suggesting that obesity may be interfering with the ability to detect early-stage prostate cancer.
  
  
  METHODS
  Dual X-ray absorptiometry (DXA) is considered a gold-standard measurement of body composition. We investigated the association between PSA levels and body composition measured by DXA among 1,360 men participating in NHANES (2001-2004), a representative sample of the U.S. male population.
  
  
  RESULTS
  After controlling for age, race, and other factors, PSA concentration was approximately 15% lower for men with the highest level of total mass, lean mass, fat mass, trunk lean mass, and trunk fat mass (all P for trend <0.05). We then multiplied PSA concentration by estimated plasma volume to calculate the amount of PSA in circulation (i.e., PSA mass). Total body fat mass and fat mass located in the body trunk were not significantly associated with PSA mass, however, PSA mass was approximately 10-15% higher across low versus high categories of total body lean mass and bone mineral content (all P-trend <0.05).
  
  
  CONCLUSIONS
  Our results using DXA to measure body composition confirm that a greater body mass, not just fat mass, is associated with a lower PSA concentration. This is consistent with PSA hemodilution within men with a higher body mass index. The separate associations between measured lean and fat mass on calculated PSA mass require further investigation.
authors.affiliation: Division of Epidemiology, Vanderbilt University Medical Center, Nashville, Tennessee 37203, USA. jay.fowke@vanderbilt.edu
authors.forename: Jay H
authors.initials: JH
authors.lastname: Fowke
authors.forename: Charles E
authors.initials: CE
authors.lastname: Matthews
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition; D055088:Early Detection of Cancer; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D009765:Obesity / Q000097:blood* / Q000150:complications; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000150:complications / Q000175:diagnosis
chemical_list: D017430:Prostate-Specific Antigen