NR602_ Midterm_ Study_ Guide 2021. Menstrual cycle physiology The initiation of menstruation, called menarche, usually happens between the ages of 12 and 15. Menstrual cycles typically continue to age 45 to 55, when menopause occurs. Many women find themselves reluctant to discuss the existence and normality of menstruation. The word menstruation has been replaced by a variety of euphemisms, such as the curse, my period, my monthly, my friend, the red flag, or on the rag. Most women exper...