2. Irregular Menstrual Cycle
Long before a woman experiences her last menstrual period due to menopausal changes in her body, she will experience a highly irregular menstrual cycle.
All women are born with a finite number of oocytes, which are immature egg cells. Starting with a girl’s menarche, each month one ovum will be expelled from the ovaries to the Fallopian tubes where they will wait to be fertilized. At this point, the uterus and endometrium undergo specific changes in order to become ready to accept a pregnancy. If no fertilization occurs, the egg is expelled from the uterus along with the remains of the endometrium, and menstruation occurs.
This entire process is orchestrated by hormonal action, which is responsible for activating the various phases that make up the human menstrual cycle. When this particular hormonal cascade, of which estrogen and progesterone play a fundamental role, is altered by menopause the cycle loses all sense of regularity and periods may begin to arrive either too late or too early.
Because hormonal levels do not fall precipitously, but rather do so progressively over a few years leading up to menopause, women will experience irregular cycles long before menopause finishes.