title: Comparative assessment in young and elderly men of the gonadotropin response to aromatase inhibition.
abstract: BACKGROUND
  Aging in men is associated with a decline in serum testosterone (T) levels.
  
  
  OBJECTIVE
  Our objective was to assess whether decreased T in aging might result from increased estradiol (E2) negative feedback on gonadotropin secretion.
  
  
  METHODS
  We conducted a comparative intervention study (2004) in the Outpatient Endocrinology Clinic, Ghent University Hospital.
  
  
  METHODS
  Participants included healthy young and elderly men (n = 10 vs. 10).
  
  
  METHODS
  We used placebo and letrozole (2.5 mg/d) for 28 d, separated by 2 wk washout.
  
  
  METHODS
  We assessed changes in serum levels of free E2, LH, and FSH, free T, SHBG, and gonadotropins response to an i.v. 2.5-microg GnRH bolus.
  
  
  RESULTS
  As assessed after 28 d of treatment, letrozole lowered E2 by 46% in the young men (P = 0.002) and 62% in the elderly men (P < 0.001). In both age groups, letrozole, but not placebo, significantly increased LH levels (339 and 323% in the young and the elderly, respectively) and T (146 and 99%, respectively) (P value of young vs. elderly was not significant). Under letrozole, peak LH response to GnRH was 152 and 52% increase from baseline in young and older men, respectively (P = 0.01).
  
  
  CONCLUSIONS
  Aromatase inhibition markedly increased basal LH and T levels and the LH response to GnRH in both young and elderly men. The observation of similar to greater LH responses in the young compared with the elderly does not support the hypothesis that increased restraining of LH secretion by endogenous estrogens is instrumental in age-related decline of Leydig cell function.
authors.affiliation: Department of Endocrinology, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium. guy.tsjoen@ugent.be
authors.forename: Guy G
authors.initials: GG
authors.lastname: T'Sjoen
authors.forename: Vito A
authors.initials: VA
authors.lastname: Giagulli
authors.forename: Hans
authors.initials: H
authors.lastname: Delva
authors.forename: Patricia
authors.initials: P
authors.lastname: Crabbe
authors.forename: Dirk
authors.initials: D
authors.lastname: De Bacquer
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Kaufman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D047072:Aromatase Inhibitors / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004958:Estradiol / Q000097:blood; D025461:Feedback, Physiological; D006062:Gonadotropins / Q000097:blood*; D006801:Humans; D000077289:Letrozole; D008297:Male; D009570:Nitriles / Q000494:pharmacology*; D014230:Triazoles / Q000494:pharmacology*
chemical_list: D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors; D006062:Gonadotropins; D009570:Nitriles; D014230:Triazoles; D004958:Estradiol; D000077289:Letrozole