If you’re a postmenopausal women looking to keep your brain sharp (really, isn’t everyone?), a growing body of research shows that taking estrogen is probably not the way to go, even if you ask for a prescription as soon as your menstrual periods start to dwindle. On the other hand, postmenopausal hormone therapy won’t dull your brain, either, according to a new study out this week. That’s reassuring for women who opt for estrogen to relieve symptoms such as hot flashes, which, along with prevention of osteoporosis, are the only Food and Drug Administration-approved reasons for going on the hormone. The latest study on this topic, published online by the journal Neurology , investigated whether taking estrogen around the time of the menopause transition protects the brain, while going on it later doesn’t. The timing hypothesis has been circulating for at least a decade and a half or so, ever since the landmark Women’s Health Initiative (WHI) concluded that menopausal