But oestrogen also makes you smarter, say US researchers who recently presented their findings at the Neuroscience 2010 conference in San Diego. And thanks to their discovery, new treatment for memory-related conditions such as Alzheimer's disease could be on the horizon.
The scientists go as far as describing oestrogen as an elixir for the brain, such is its effectiveness at sharpening mental performance. According to the researchers it dramatically increases the number of connections between brain cells (neurons), which are called dentritic spines (tiny bridges that allow brain cells to talk to one another).
And of course the more neural connections you have, the better your mental performance. In fact, people with Alzheimer's disease often have a smaller number of dentritic spines than others.
But there's a problem with treating people using oestrogen. Several studies suggest that long-term use of HRT - which includes oestrogen - for menopausal symptoms could be linked with an increased risk of cancer, heart disease and stroke.
However the scientists believe they've overcome any such difficulties. They have developed a special compound that activates the brain's oestrogen receptors. So you can get the benefits of oestrogen without the risks.
Oestrogen levels are generally at their highest in the week before your period. We're not convinced we're more intelligent then than at other times. Are you?