Menstrual Cycle

The expulsion of tissue and blood from the uterus lasts from three to eight days, with much variation among women. Some women experience painful cramps during menstruation, which are the result of uterine contractions that expel the endometrium. Hormones known as prostaglandins are produced by uterine cells during menstruation, and the excessive production of prostaglandins is associated with stronger uterine contractions and more intense cramps. Menstrual cramps can be treated by drugs that inhibit the production of prostaglandins in uterine cells. Aspirin, ibuprofin, and naproxin sodium are all effective anti-prostaglandin drugs. It is important to take these medications at the onset of the menstrual flow, otherwise prostaglandin production can proceed for several hours unchecked, and the drugs will not be effective in reducing pain.

Some women also experience premenstrual syndrome (PMS), a condition occurring some time in the secretory phase prior to menstruation. Symptoms of PMS include mood changes, water retention and bloating, increase in appetite and cravings, cramps, breast pain, and headaches. Researchers are not sure what causes PMS, but the sharp drop in progesterone that occurs at about day 22 may be involved in triggering these physical and emotional symptoms. While no cure for PMS exists, experts recommend that women who experience PMS reduce their salt intake, engage in more exercise, and maintain a healthy diet during this time. The B vitamins may also be effective in reducing PMS symptoms. Some women have found relief in taking the medications prescribed for menstrual cramps, while lowering caffeine intake can be useful in reducing premenstrual breast pain.

Girls begin menstruating at the onset of puberty, at about the age of 12 or 13, although the onset of menstruation may be earlier or later, depending on the amount of body fat. The first menstrual period is called the menarche; during the first few cycles, ovulation may be absent.

Menopause is the cessation of the menstrual cycle, when ovulation and menstruation cease. The cessation of menstruation is gradual and is preceded by menstrual cycles in which ovulation does not occur. The menstrual cycle becomes irregular before finally stopping completely. The onset of menopause is individually variable, occurring between the ages of 45 to the late fifties.