Our interest in this area stemmed from clinical observations that estrogen acts beyond its traditional targets in the hypothalamus and pituitary, and influences other facets of brain function involved in memory and
neurodegeneration. Since neurodegenerative events occur frequently in elderly women who are chronically hypoestrogenic, the results of these studies carry profound implications in the clinical setting. Thus, it is important, to determine Inhibitors,research,lifescience,medical whether and how ERT can ameliorate neural dysfunction. Estrogen and cognition Clinical studies demonstrate that estrogen influences memory and cognition,6,17-22 and can protect against neurodegenerative diseases such as AD.10,11,23-30 These findings, however, are not without Inhibitors,research,lifescience,medical controversy. As the results of more clinical studies become available, we are beginning to appreciate that, the protective actions of estrogen do not apply in all situations.31-33 Many studies have examined whether ERT
improves cognitive function. The majority of data show that estrogen can enhance cognitive function in both young22 and Inhibitors,research,lifescience,medical older women.19,21,34 It appears that by maintaining normal cognitive function, estrogen may further act to decrease the risk and delay the onset, of AD.10,26,28-35 Importantly, estrogen docs not exert actions on all aspects of memory. It is critical to consider that memory is a broad term describing several distinct neural functions, many Inhibitors,research,lifescience,medical of which originate in different and overlapping regions of the brain. Thus, it is not surprising that estrogen may learn more influence specific subtypes of memory. For example, some,17,19,34 but not all,36 studies show that ERT appears to specifically enhance immediate and delayed recall of verbal information. Other reports indicate that the beneficial actions of ERT on cognition include improvement of visuospatial memory.37,38
Estrogen and Alzheimer’s disease Several studies have examined whether ERT decreases the risk, delays the onset, or stops the progression of neurodegeneration caused by AD. Estrogen has been shown to decrease Inhibitors,research,lifescience,medical the risk for AD10 or induce a modest improvement, in cognitive function in individuals with AD.11,35,39,40 However, other studies have reported no difference in cognitive function also between estrogen- and placebo-treated individuals.41-43 A recent cohort, study43 failed to detect slowing of AD progression or improvement of cognitive and functional outcomes in women with mild-to-modcratc AD treated with Premarin®. The results of this study and those of other studies31-33 strongly suggest, that estrogen may fail to reverse or even halt a disease process that has already been initiated. Therefore, while it is clear that estrogen can influence certain aspects of cognitive function and decrease the risk for AD, it remains controversial whether it can act against an existing neurodegenerative condition. Taken together, the findings of these studies indicate that estrogen may protect the brain through primary prevention.