title: Pubertal upregulation of erythropoiesis in boys is determined primarily by androgen.
abstract: OBJECTIVE
  To study the relative roles of androgens and the growth hormone-insulin-like growth factor I (GH-IGF-I) system in the regulation of erythropoiesis in boys during puberty.
  
  
  METHODS
  We treated 23 boys with constitutional delay of puberty with low-dose testosterone (T), in combination with either a potent aromatase inhibitor, letrozole (Lz; 2.5 mg/d), or placebo (P). The study design was randomized, double-blinded, and placebo-controlled between the treated groups. Treatment with T + Lz was associated with high T and low IGF-I concentrations, whereas treatment with T + P resulted in moderately increased T and high IGF-I concentrations.
  
  
  RESULTS
  The blood hemoglobin concentration increased by 1.6 g/dL in T + Lz-treated boys, despite their low IGF-I concentrations. The estimated red blood cell volume increased more in T + Lz-treated than in T + P-treated boys (349 vs 174 mL, respectively, P = .01). Serum T concentrations during the treatment period correlated with the 12-month increments in hemoglobin and red blood cell volume. The changes in blood hemoglobin concentration and RBC in T + Lz-treated boys were similar to those we observed in a population of normal adolescent boys in the late stages of puberty.
  
  
  CONCLUSIONS
  The pubertal increase in hemoglobin concentration in boys is related to direct androgen effects.
authors.affiliation: Hospital for Children and Adolescents, University of Helsinki, Helsinki, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Hero
authors.forename: Sanna
authors.initials: S
authors.lastname: Wickman
authors.forename: Raija
authors.initials: R
authors.lastname: Hanhijärvi
authors.forename: Martti A
authors.initials: MA
authors.lastname: Siimes
authors.forename: Leo
authors.initials: L
authors.lastname: Dunkel
mesh_terms: D000293:Adolescent; D000728:Androgens / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D047072:Aromatase Inhibitors / Q000627:therapeutic use; D002648:Child; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism; D004920:Erythropoiesis / Q000187:drug effects*; D013006:Growth Hormone / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000502:physiology; D000077289:Letrozole; D008297:Male; D009570:Nitriles / Q000627:therapeutic use*; D011627:Puberty / Q000502:physiology; D011628:Puberty, Delayed / Q000188:drug therapy* / Q000378:metabolism; D013739:Testosterone / Q000097:blood / Q000378:metabolism / Q000627:therapeutic use*; D016896:Treatment Outcome; D014230:Triazoles / Q000627:therapeutic use*; D015854:Up-Regulation
chemical_list: D000728:Androgens; D047072:Aromatase Inhibitors; D006454:Hemoglobins; D009570:Nitriles; D014230:Triazoles; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D000077289:Letrozole; D013006:Growth Hormone