Dr. Mary Claire Haver

So...

In a normal, healthy woman, we have this very predictable ebb and flow of estrogen, progesterone, LH, and FSH.

And it's very predictable.

On day 12, they're going to look like this.

On day 18, they're going to look like that.

On day 21, and so on and so on, unless she's pregnant or suppressing her periods for some reason.

So in perimenopause begins when we reach a critical egg threshold level.

where those signals from the brain no longer work like they used to.

The signals go down, bind to whatever eggs are left, but they're not getting that robust response yet because of how many are left.

So the brain starts getting very upset and saying, where's my estrogen?

It's time.

We're on day 28.

We should start, this should be happening.

And the ovaries are like,

I'm doing all I can.

So the brain starts sending higher and higher levels of that FSH and LH in order to force the ovulation.

So what happens is you end up getting sometimes two ovulations in one month.

You get these very erratic levels, much higher estradiol levels than we ever had outside of pregnancy.

Then they crash down and progesterone can never quite keep up.

So what used to look like that beautiful, predictable EKG-like