How Young Do You Have To Be Before You Start Expieriencing Menopause?

The average age for menopause in the U.S. as defined by three consecutive months of no menstruation is age 49.
Menopause is not something visited upon you one night by the menopause fairy, rather it is a process that probably starts for most women in their early thirties. There is a typical shortening of menstral cycle and then a lengthening of menstral cycle before it ceases entirely. Some women do go through menopause earlier than others and this often correlates to girls who started puberty earlier.
Many of the symptoms associated with menopause can be improved with low doses of oral estrogen (HRT). There is some information that HRT increases the risk of breast and ovarian cancer. I believe there are other studies that conflict with that conclusion, however.