abstract: Differences in regional brain metabolism associated with specific formulations of hormone therapy in postmenopausal women at risk for AD (Alzheimer's disease)

"In conclusion, particular areas of relatively preserved metabolism were seen in women with more years of endogenous estrogen exposure, as well as in women taking estradiol-based formulations or estrogen therapies unopposed by progesterone, together suggesting regionally specific neuroprotective estrogenic effects."