Objective: To evaluate and compare the effects or oral and transdermal estrogen replacement therapy on biochemical markers of bone resorption in early postmenopausal women.
Design: Controlled, randomized group comparison.
Setting: Outpatient clinic for menopausal women and research into osteoporosis.
Subjects: Sixty healthy women menopausal for less than 5 years and who had never received any medications interfering with bone metabolism.
Interventions: The 60 women were randomly allocated to 3 months therapy with either oral conjugated estrogens (0.625 mg/day) (n = 28) or transdermal estradiol (50 micrograms/day) (n = 32) in cyclical combination with medroxyprogesterone acetate (5 mg/day).
Main outcome measures: Traditional (urinary calcium/creatinine and hydroxyproline/creatinine) and the new specific (urinary pyridinoline/creatinine and deoxypyridinoline/creatinine) markers of bone resorption were determined before and after 3 months of treatment.
Results: In both groups, circulating levels of estrone and estradiol were significantly (P < 0.001) increased during treatment. In women treated with oral conjugated equine estrogens, urinary calcium/creatinine and hydroxyproline/creatinine ratios were significantly (P < 0.05) reduced. Pyridinoline/creatinine ratio fell from 69.1 (4) [mean (SEM)] to 50 (4) mumol/mumol (P < 0.01) and deoxypyridinoline/creatinine ratio fell from 10.8 (1) [mean (SEM)] to 8.3 (0.8) mumol/mumol (P < 0.01). In the group treated with transdermal estradiol, urinary hydroxyproline/creatinine ratio was significantly (P < 0.05) reduced. Pyridinoline/creatinine ratio fell from 66.3 (4) [mean (SEM)] to 46.2 (3) mumol/mumol (P < 0.01) and deoxypyridinoline/creatinine ratio fell from 11.5 (1.5) [mean (SEM)] to 7.7 (0.6) mumol/mumol (P < 0.01). There were no differences between the evolution of the biochemical variables in the two groups.
Conclusion: These results suggest that oral conjugated equine estrogens and transdermal estradiol, in the given doses, are equally effective in reducing postmenopausal bone resorption.