Effects of tibolone on endogenous nitric oxide (nitrite/nitrate levels) in postmenopausal women.
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.
Akgül
Cemil
C
Department of Obstetrics and Gynecology, Istanbul Medical Faculty, Turkey.
Canbaz
Mukaddes
M
Vural
Pervin
P
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
D020847:Estrogen Receptor Modulators; D009652:Norpregnenes; D009569:Nitric Oxide; C027385:tibolone