EFFECTS OF HORMONE REPLACEMENT THERAPY ON PLATELET MEMBRANE FATTY-ACID COMPOSITION

Oestrogen replacement therapy has been shown to protect postmenopausal women from ischaemic heart disease, strokes and hypertension. The mec hanism of protection conferred by oestrogen, although partly attributa ble to changes in serum lipoproteins, is not fully understood. The pre sent study was undertaken to assess the effect of hormone replacement therapy on the composition of platelet membrane fatty acids in postmen opausal women. These were analysed by gas-liquid chromatography before and six weeks after continuous conjugated equine oestrogen therapy (0 .625 mg daily) combined with cyclical therapy with 75 mu g L-norgestre l from day 17 to 28 of a 28-day cycle. Each subject acted as her own c ontrol. The principal findings of the study were that, following treat ment, there was a 16.2% reduction in platelet membrane polyunsaturated fatty acids (P < 0.001), an increase of 9.1 and 7.1% in saturated fat ty acids and monounsaturated fatty acids respectively (P < 0.001) and a 17.8% reduction in arachidonic acid (P < 0.003). There was no correl ation between changes in membrane fatty acids and serum lipoproteins. This suggests that the changes in membrane composition noted in this s tudy may be a primary effect of hormone replacement therapy, especiall y oestrogen.