Starting menstrual periods at a younger age is associated with an increased risk of endometrial cancer.

The earlier a woman’s periods start, the higher her risk of endometrial cancer. The risk increases by about 2% with each year younger a woman is when she starts having periods. For example, the risk of endometrial cancer in a woman who has her first period at age 11 is about 4% higher than for a woman who has her first period at age 13.

The increased risk of endometrial cancer in women whose periods start at a younger age is likely to be due to hormones. Women whose periods start earlier are exposed to the female hormone oestrogen for longer than women whose periods start at an older age. Starting periods at an older age reduces the number of menstrual cycles a women experiences during her lifetime and therefore her risk of endometrial cancer.