C h a p t e r 4 0
Disorders of the Female Genitourinary System
1021
(FSH) and luteinizing hormone (LH) from the anterior
pituitary gland
3,4
(Fig. 40-6). Because these hormones
promote the growth of cells in the ovaries and testes
as a means of stimulating the production of sex hor-
mones, they are called the
gonadotropic hormones
. The
secretion of LH and FSH is stimulated by gonadotro-
pin-releasing hormone (GnRH) from the hypothalamus.
These gonadotropins then trigger the ovary to release an
oocyte that is capable of being fertilized. Concurrently,
the ovary secretes hormones that act on the endome-
trial lining of the uterus to prepare for implantation.
In addition, the ovarian hormones provide feedback to
the hypothalamus and pituitary regarding the secretion
of gonadotropins during the menstrual cycle.
In addition to LH and FSH, the anterior pituitary
secretes a third reproductive hormone called
prolactin
.
The primary function of prolactin is the stimulation of
lactation in the postpartum period. During pregnancy,
prolactin, along with other hormones such as estrogen,
progesterone, insulin, and cortisol, contributes to breast
development in preparation for lactation. Although
prolactin does not appear to play a physiologic role in
ovarian function, hyperprolactinemia can lead to hypo-
gonadism. This may include an initial shortening of the
luteal phase with subsequent absence of menstruation,
scanty menstruation, infrequent menstruation (periods
more that 35 days apart), and infertility. The hypotha-
lamic control of prolactin secretion is primarily inhibi-
tory, and dopamine is the most important inhibitory
factor. Hyperprolactinemia may occur as an adverse
effect of drug treatment using phenothiazine derivatives
(i.e., antipsychotic drugs that block dopamine receptors).
Ovarian Hormones
The ovaries produce estrogens, progesterone, and andro-
gens (e.g., testosterone). In the ovary, the main source of
hormone production are the maturing follicles, includ-
ing the theca cells and granulosa cells (Fig. 40-7A),
and the corpus luteum, the cell mass remaining in the
ovary after the oocyte has been released (Fig. 40-7B).
The theca cells produce androgens, the granulosa cells
produce estrogen, and the corpus luteum produces pro-
gesterone. The other stromal cells that contribute to the
production of androgens can be divided into two popu-
lations: the secondary interstitial cells (derived from the
theca) and the cells of the hilum, the bridge of tissue
through which blood vessels and nerves enter and exit
the ovary (see Fig. 40-7B). These cells are the major ones
involved in androgen production during menopause.
3,4
Estrogens.
Estrogens are a family of structurally related
female sex hormones synthesized and secreted by cells in
the ovaries and, in small amounts, by cells in the adre-
nal cortex.
3–5
Androgens can be converted to estrogens
peripherally, especially in adipose tissue. Three estro-
gens occur naturally in humans: estrone, estradiol, and
estriol. Of these, estradiol is the most biologically potent
and the most abundantly secreted product of the ovary.
Estrogens are transported in the blood bound to spe-
cific plasma globulins, inactivated and conjugated in the
liver, and then excreted in the bile.
Estrogens are necessary for normal female develop-
ment.
3–5
They stimulate the development of the vagina,
uterus, and uterine tubes in the embryo. They also stim-
ulate the stromal development and ductal growth of the
breasts at puberty, are responsible for the accelerated
pubertal skeletal growth phase and for closure of the
epiphyses of the long bones, contribute to the growth
of axillary and pubic hair, and alter the distribution of
body fat to produce the typical female body contours.
In concert with other hormones, estrogens provide for
the reproductive processes of ovulation, implantation of
the products of conception, pregnancy, parturition, and
lactation by stimulating the development and maintain-
ing the growth of the reproductive organs.
Estrogens also have a number of other important met-
abolic effects. They are responsible for maintaining the
normal structure of skin and blood vessels in women.
Estrogens decrease the rate of bone resorption by antago-
nizing the effects of calcitonin on bone; for this reason,
osteoporosis is a common problem in estrogen-deficient
postmenopausal women (see Chapter 44). In the liver,
estrogens increase the synthesis of transport proteins for
thyroxine, estrogen, testosterone, and other hormones.
Estrogens also affect the composition of the plasma
Hypothalamus
Anterior
pituitary
Ovary
GnRH
Feedback
Target tissues
Target tissues
Cerebral cortex, limbic system
and other brain centers
Estrogen
Progestin
LH
FSH
Theca
interna
Corpus
luteum
FIGURE 40-6.
Hypothalamic-pituitary feedback control of
estrogen and progesterone levels in the female.The dashed
line represents negative feedback. FSH, follicle-stimulating
hormone; GnRH, gonadotropin-releasing hormone; LH, luteinizing
hormone.
