Effects of tibolone or continuous combined oestradiol and norethisterone acetate on lipids, HDL subfractions and apolipoproteins in post-menopausal women in a two-year, randomised, double-blind, placebo-controlled trial.
To compare the effects of 1) tibolone, 2) continuous combined oestrogen plus progestogen and 3) placebo on plasma lipid and lipoprotein markers of cardiovascular risk in healthy post-menopausal women.randomised, single-centre, placebo-controlled, double-blind study PATIENTS: 101 post-menopausal women were randomised (1:1:1) into one of three groups taking daily 2.5mg tibolone, continuous oral oestradiol-17β 2mg plus norethisterone acetate 1mg daily (E2 /NETA) or placebo.Fasting serum lipid, lipoprotein and apolipoprotein concentrations measured at baseline and after 6, 12 and 24 months of treatment.Both tibolone and E2 /NETA lowered plasma total cholesterol concentrations relative to placebo. With tibolone, high-density lipoprotein cholesterol (HDL-C) was reduced (-27% at 24 months, p<0.001), the greatest effect being in the cholesterol-enriched HDL2 subfraction (-40%, p<0.001). Tibolone’s effect on HDL concentrations was also apparent in the principal HDL protein component, apolipoprotein AI (-29% at 24 months, p<0.001). However, there was no significant effect of tibolone on low-density or very-low-density lipoprotein cholesterol (LDL-C and VLDL-C, respectively). By contrast, the greatest reduction in cholesterol with E2 /NETA was in LDL-C (-22% at 24 months, p=0.008). E2 /NETA reduced HDL-C to a lesser extent than tibolone (-12% at 24 months, p<0.001). Effects on HDL apolipoproteins were similarly diminished relative to tibolone. E2 /NETA had no effect on VLDL-C or on the protein component of LDL, apolipoprotein B.Tibolone reduces serum HDL. E2 /NETA reduces LDL cholesterol but not apolipoprotein B, suggesting decreased cholesterol loading of LDL. Any impact these changes may have on CVD risk needs further investigation.