Transdermal estradiol reduces plasma myeloperoxidase levels without affecting the LDL resistance to oxidation or the LDL particle size

OBJECTIVE: This study was designed to investigate the effects of different therapeutic range doses of transdermal estradiol (E(2)), alone or in combination with progesterone (P) or medroxyprogesterone acetate (MPA), on plasma lipoprotein levels and on three parameters related with LDL oxidizability, the resistance of LDL to oxidation by copper, the LDL particle size, and the myeloperoxidase levels. DESIGN: Thirty-five healthy postmenopausal women who had been amenorrheic for at least 1 year received two consecutive, 2-month doses of transdermal estrogen (25-microg and 50-microg E(2) patch). Thereafter, they were randomly assigned to receive a 2-month treatment of either a 100-microg E(2) patch or a 50-microg E(2) patch combined with P (300 mg/day) or MPA (5 mg/day) during the last 14 days. RESULTS: Neither transdermal E(2) alone nor transdermal E(2) plus progestogen modified the lipoprotein profile, the LDL resistance to oxidation, or the LDL particle size. However, all treatments similarly reduced the myeloperoxidase protein levels. CONCLUSIONS: Different dosages of transdermal E(2) within the therapeutic range were equally effective in reducing myeloperoxidase protein levels. The effect remained after addition of P or MPA in a sequential regime.