title: Effects of tibolone on endogenous nitric oxide (nitrite/nitrate levels) in postmenopausal women.
abstract: OBJECTIVE
  To observe the effects of hormone replacement therapy with 2.5 mg/day tibolone for 6 months upon plasma nitrite/nitrate (end products of nitric oxide metabolism) in postmenopausal women.
  
  
  METHODS
  The study involved 24 healthy postmenopausal women treated with tibolone (2.5 mg/day for 6 months) and 20 postmenopausal women who received placebo. Plasma nitrite/nitrate levels were measured with the Griess reaction. Statistical significance was analyzed by the Mann-Whitney U test and Pearson correlation analysis.
  
  
  RESULTS
  The mean baseline concentrations of nitrite/nitrate were similar in both treated and placebo groups. Tibolone treatment decreased plasma nitrite/nitrate levels.
  
  
  CONCLUSIONS
  We suggest that because of its androgenic and progestogenic actions, tibolone diminishes nitrite/nitrate levels. Also our data provide evidence for the existence of increased (1/3 of subjects, n = 8) and reduced (2/3 of subjects, n = 16) nitrite/nitrate levels in response to tibolone treatment. Clearly, further studies are necessary to establish a risk/benefit ratio for tibolone in view of its effects on nitric oxide metabolism.
authors.affiliation: Department of Obstetrics and Gynecology, Istanbul Medical Faculty, Turkey.
authors.forename: Cemil
authors.initials: C
authors.lastname: Akgül
authors.forename: Mukaddes
authors.initials: M
authors.lastname: Canbaz
authors.forename: Pervin
authors.initials: P
authors.lastname: Vural
mesh_terms: D020847:Estrogen Receptor Modulators / Q000494:pharmacology*; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D008875:Middle Aged; D009569:Nitric Oxide / Q000097:blood*; D009652:Norpregnenes / Q000494:pharmacology*; D017698:Postmenopause; D018709:Statistics, Nonparametric
chemical_list: D020847:Estrogen Receptor Modulators; D009652:Norpregnenes; D009569:Nitric Oxide; C027385:tibolone