Many changes during the years leading up to menopause (perimenopause) are brought on by changing levels of hormones produced by the ovaries, mainly estrogen.

What hormones are affected by perimenopause?

As you go through perimenopause, your body's production of estrogen and progesterone, key female hormones, rises and falls. Many of the changes you experience during perimenopause are a result of decreasing estrogen.

What triggers perimenopause?

What causes perimenopause? Perimenopause is a natural process caused when your ovaries gradually stop working. Ovulation may become erratic and then stop. The menstrual cycle lengthens and flow may become irregular before your final period.