Menopause is the time after which the final menses occurs. It is associated with the cessation of ovarian function and reproductive cycles. Generally, menstrual cycles and bleeding become irregular, and the cycles become shorter from the lack of follicular development (shortened follicular phases). The ovaries atrophy and are characterized by the presence of few, if any, healthy follicles.
The decline in ovarian function is associated with a decrease in estrogen secretion and a concomitant increase in LH and FSH, which is characteristic of menopausal women (Table 38.3). It is used as a diagnostic tool. The elevated LH stimulates ovarian stroma cells to continue producing androstenedione. Estrone, derived almost entirely from the peripheral conversion of adrenal and ovarian androstene-dione, becomes the dominant estrogen (see Fig. 37.9). Because the ratio of estrogens to androgens decreases, some women exhibit hirsutism, which results from androgen excess. The lack of estrogen causes atrophic changes in the breasts and reproductive tract, accompanied by vaginal dryness, which often causes pain and irritation. Similar changes in the urinary tract may give rise to urinary disturbances. The epidermal layer of the skin becomes thinner and less elastic.
Hot flashes, as a result of the loss of vasomotor tone, osteoporosis, and an increased risk of cardiovascular disease are not uncommon. Hot flashes are associated with episodic increases in upper body and skin temperature, peripheral va-sodilation, and sweating. They occur concurrently with LH pulses but are not caused by the gonadotropins because they are evident in hypophysectomized women. Hot flashes, consisting of episodes of sudden warmth and sweating, reflect temporary disturbances in the hypothalamic thermoregula-tory centers, which are somehow linked to the GnRH pulse generator.
Osteoporosis increases the risk of hip fractures and estrogen replacement therapy reduces the risk. Estrogen antagonizes the effects of PTH on bone but enhances its effect on kidney, i.e., it stimulates retention of calcium. Estrogen also promotes the intestinal absorption of calcium through 1,25-dihydroxyvitamin D3.
Menopausal symptoms are often treated with hormone replacement therapy (HRT), which includes estrogens and progestins. HRT is not an uncommon treatment to improve the quality of life. In some patients, treatment with estrogen can cause adverse effects, such as vaginal bleeding, nausea, and headache. Estrogen therapy is contraindicated in cases of existing reproductive tract carcinomas or hypertension and other cardiovascular disease. The prevailing opinion is that the benefit of treating postmenopausal women with estrogens for limited periods outweighs any risk of developing breast or endometrial carcinomas.
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