The effect of the plasma oestradiol concentration on climacteric symptoms gonadotrophin release, and bone resorption was studied in three groups of postmenopausal women given 0.025 mg, 0.05 mg, or 0.1 mg transdermal oestradiol daily. There was a dose related reduction in symptoms, plasma follicle stimulating hormone concentration, and urinary calcium and hydroxyproline excretion. The relation of the response to plasma oestradiol values was similar for each variable with an initial large reduction and little change in response to increases in the plasma oestradiol concentration above 150 pmol/1 (41 pg/ml). Hormone replacement therapy producing an effect equivalent to higher oestradiol concentrations is likely to increase the risk of side effects without conferring any additional benefit.
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