860
UNIT SIX
istics may change. The breasts, vagina, uterus, and uterine
tubes may shrink, and the pubic and axillary hair may thin.
The epithelial linings associated with urinary and reproduc-
tive organs may thin. There may be increased loss of bone
matrix (osteoporosis) and thinning of the skin. The pituitary
secretions of FSH and LH are no longer inhibited, so these
hormones may be continuously released for some time.
About 50% of women reach menopause by age ± fty, and
85% reach it by age ± fty-two. Of these, perhaps 20% have
no unusual health effects—they simply stop menstruating.
However, about 50% of women experience unpleasant vaso-
motor signs during menopause, including sensations of heat
in the face, neck, and upper body called “hot fl ashes.” Such a
sensation may last for thirty seconds to ± ve minutes and may
Menopause
After puberty, reproductive cycles continue at regular inter-
vals into the late forties or early ±
fties, when they usually
become increasingly irregular. Then within a few months or
years, the cycles cease. This period in life is called
meno-
pause
(men
o-pawz), or female climacteric.
Aging of the ovaries causes menopause. After about
thirty-±
ve years of cycling, few primary follicles remain to
respond to pituitary gonadotropins. The follicles no longer
mature, ovulation does not occur, and the blood concentra-
tion of estrogens plummets, although many women continue
to synthesize some estrogens from adrenal androgens.
As a result of reduced concentrations of estrogens and
lack of progesterone, the female secondary sex character-
FIGURE 22.33
Major events in the female reproductive cycle.
Days
Days
Menstruation
Menstruation
Proliferative phase
Secretory phase
1
LH
Estrogens
Estrogens
Progesterone
Progesterone
Developing
follicle
Follicular phase
Luteal phase
Corpus
albicans
Ovulation
Mature
follicle
Early
corpus luteum
Regressive
corpus luteum
Plasma hormonal
concentration
Plasma hormonal
concentration
Ovarian events
Thickness of endometrium
FSH
FSH
LH
Ovarian activity
Uterine activity
7
1
3
5
9
1
11
31
51
71
92
12
32
52
7
21
28
13
7
14
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