title: Effects of graded doses of testosterone on erythropoiesis in healthy young and older men.
abstract: BACKGROUND
  Erythrocytosis is a dose-limiting adverse effect of testosterone therapy, especially in older men.
  
  
  OBJECTIVE
  Our objective was to compare the dose-related changes in hemoglobin and hematocrit in young and older men and determine whether age-related differences in erythropoietic response to testosterone can be explained by changes in erythropoietin and soluble transferrin receptor (sTfR) levels.
  
  
  METHODS
  We conducted a secondary analysis of data from a testosterone dose-response study in young and older men who received long-acting GnRH agonist monthly plus one of five weekly doses of testosterone enanthate (25, 50, 125, 300, or 600 mg im) for 20 wk.
  
  
  METHODS
  The study took place at a General Clinical Research Center.
  
  
  METHODS
  Participants included 60 older men aged 60-75 yr and 61 young men aged 19-35 yr.
  
  
  METHODS
  Outcome measures included hematocrit and hemoglobin and serum erythropoietin and sTfR levels.
  
  
  RESULTS
  Hemoglobin and hematocrit increased significantly in a linear, dose-dependent fashion in both young and older men in response to graded doses of testosterone (P<0.0001). The increases in hemoglobin and hematocrit were significantly greater in older than young men. There was no significant difference in percent change from baseline in erythropoietin or sTfR levels across groups in either young or older men. Changes in erythropoietin or sTfR levels were not significantly correlated with changes in total or free testosterone levels.
  
  
  CONCLUSIONS
  Testosterone has a dose-dependent stimulatory effect on erythropoiesis in men that is more pronounced in older men. The testosterone-induced rise in hemoglobin and hematocrit and age-related differences in response to testosterone therapy may be mediated by factors other than erythropoietin and sTfR.
authors.affiliation: Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, 670 Albany Street, 2nd Floor, Boston, Massachusetts 02118, USA. andrea.coviello@bmc.org
authors.forename: Andrea D
authors.initials: AD
authors.lastname: Coviello
authors.forename: Beth
authors.initials: B
authors.lastname: Kaplan
authors.forename: Kishore M
authors.initials: KM
authors.lastname: Lakshman
authors.forename: Tai
authors.initials: T
authors.lastname: Chen
authors.forename: Atam B
authors.initials: AB
authors.lastname: Singh
authors.forename: Shalender
authors.initials: S
authors.lastname: Bhasin
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D004305:Dose-Response Relationship, Drug; D004920:Erythropoiesis / Q000187:drug effects*; D004921:Erythropoietin / Q000097:blood; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011990:Receptors, Transferrin / Q000032:analysis; D013739:Testosterone / Q000494:pharmacology*
chemical_list: D006454:Hemoglobins; D011990:Receptors, Transferrin; D004921:Erythropoietin; D013739:Testosterone