Women, like men, go through a midlife change in hormone secretion called the climacteric. In women, it is accompa
26men = monthly
27 pro = favoring + gest = pregnancy + sterone = steroid hormone nied by menopause, the cessation of menstruation (see insight 28.2).
With age, the ovaries have fewer remaining follicles and those that remain are less responsive to gonadotropins. Consequently, they secrete less estrogen and progesterone. Without these steroids, the uterus, vagina, and breasts atrophy. Intercourse may become uncomfortable, and vaginal infections more common, as the vagina becomes thinner, less distensible, and drier. The skin becomes thinner, cholesterol levels rise (increasing the risk of cardiovascular disease), and bone mass declines (increasing the risk of osteoporosis). Blood vessels constrict and dilate in response to shifting hormone balances, and the sudden dilation of cutaneous arteries may cause hot flashes—a spreading sense of heat from the abdomen to the thorax, neck, and face. Hot flashes may occur several times a day, sometimes accompanied by headaches resulting from the sudden vasodilation of arteries in the head. In some people, the changing hormonal profile also causes mood changes. Many physicians prescribe hormone replacement therapy (HRT)—low doses of estrogen and progesterone taken orally or by a skin patch—to relieve some of these symptoms. The risks and benefits of HRT are still being debated.
_Think About It_
FSH and LH secretion rise at climacteric and these hormones attain high concentrations in the blood. Explain this using the preceding information and what you know about the pituitary-gonadal axis.
Menopause is the cessation of menstrual cycles, usually occurring between the ages of 45 and 55. The average age has increased steadily in the last century and is now about 52. It is difficult to precisely establish the time of menopause because the menstrual periods can stop for several months and then begin again. Menopause is generally considered to have occurred when there has been no menstruation for a year or more.
Insight 28.2 Evolutionary Medicine
There has been considerable speculation about why women do not remain fertile to the end of their lives, as men do. Some theorists argue that menopause served a biological purpose for our prehistoric fore-mothers. Human offspring take a long time to rear. Beyond a certain point, the frailties of age make it unlikely that a woman could rear another infant to maturity or even survive the stress of pregnancy. She might do better in the long run to become infertile and finish rearing her last child instead of having another one. In this view, menopause was biologically advantageous for our ancestors—in other words, an evolutionary adaptation.
Saladin: Anatomy & I 28. The Female I Text I I © The McGraw-Hill
Physiology: The Unity of Reproductive System Companies, 2003 Form and Function, Third Edition
Others argue against this hypothesis on the grounds that Ice Age skeletons indicate that early hominids rarely lived past age 40. If this is true, menopause setting in at 45 to 55 years of age could have served little purpose. In this view, Ice Age women may indeed have been fertile to the end of their lives; menopause now may be just an artifact of modern nutrition and medicine, which have made it possible for us to live much longer than our ancestors did.
Before You Go On
Answer the following questions to test your understanding of the preceding section:
5. Describe the similarities and differences between male and female puberty.
6. Describe the major changes that occur in female climacteric and the principal cause of these changes.
7. What is the difference between climacteric and menopause?
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