Plasma oestrogen fractions in postmenopausal women receiving hormone replacement therapy: influence of route of administration and cigarette smoking

The: aim of this study was to determine the impact of the administration ro ute and cigarette smoking on plasma oestrogen levels during oral and parent eral oestrogen replacement therapy (ERT). Fourteen healthy postmenopausal w omen (six smokers and eight non-smokers) were recruited for a prospective, randomised, crossover study at a private outpatient medical centre in Oslo, Norway. All patients were randomised to receive cyclic therapy with oestra diol and norethisterone orally or by the transdermal route each for a 6-mon th period. Plasma levels of oestrone (Oe(1)), oestradiol (Oe(2)) and oestro ne sulphate (Oe(1)S) were determined using highly sensitive RIA methods bef ore and during hormone replacement therapy given by the oral and transderma l route. Comparing smokers and nonsmokers, plasma levels of Oe(1), Oe(2) an d Oe(1)S were all found to be 40-70% lower in smokers compared with non-smo kers when ERT was given orally (Oe(1)S, P<0.05; Oe(1) and Oe(2), P<0.01 for both). Oe(2) given orally caused a higher Oe(1)S/Oe(2) ratio but also a hi gher Oe(1)/Oe(2) ratio compared with parenteral therapy in smokers (40.2 ve rsus 7.0, P<0.01; and 3.2 versus 0.8, P<0.05 respectively). No significant differences in these parameters in the different test-situations were seen in non-smokers. Except for a lower level of Oe(1)S in smokers (non-signific ant), no difference in plasma oestrogen levels between smokers and non-smok ers was observed during parenteral therapy. In conclusion, cigarette smokin g has been shown to have major impact on plasma oestrogen levels during ora l but not during parenteral Oe(2) replacement.