Estrogen

Menopause diminishes the incidence of gynecological cancers because estrogen and progesterone are involved in the development of these cancers in the first place. During the latter part of each menstrual cycle, to prepare the body for possible pregnancy, estrogen and progesterone cause the cells lining the milk ducts in the breast to divide. Every time a cell divides, there is a chance that errors (mutations) can occur in its genetic material, so that the more cycles a woman undergoes that involve cell division of the duct cells, the greater the chance of mutations. Conversely, when these cells become specialized to produce milk during and after pregnancy, they are no longer proliferating and therefore are less likely to undergo mutations. Thus, the rise in breast cancer during the last half of the twentieth century can probably be explained in large part by changes in the length of the total reproductive period, the number of pregnancies and more common delays in having a first child. Ironically, therefore, menopause in its modern context is actually a favorable event for women's health with respect to breast cancer.

In contrast to its beneficial effect on breast cancer incidence, menopause is detrimental to numerous aspects of health. One of the major outcomes of the decline in estrogen is the increased risk of cardiovascular disease and death from heart attacks. In the United States, cardiovascular disease is the number one killer of men starting at age thirty-five, whereas in women, it is not until after the age of sixty that cardiovascular disease becomes the number one cause of death. Indeed, heart and arterial disease kill almost ten times as many postmenopausal women in Western society as do all the gynecological cancers combined.

The second major consequence of the decline in estrogen is osteoporosis, thinning and loss of bone that can ultimately lead to wrist, hip, and vertebral fractures. Both men and women lose bone as they age, but during the first five to ten years after menopause, women experience accelerated bone loss, making them much more likely than men to suffer collapse of vertebrae, wrist fractures, and broken hips. About 20 percent of elderly women with osteoporetic hip fractures die of complications within one year, ranking osteoporosis as the twelfth greatest killer in the United States. Similar to heart disease, osteoporosis is more deadly than all the gynecological cancers combined.