What are fibroids?
The official medical name for fibroids is uterine
leiomyomata. They are a growth of uterine smooth muscle
cells that reproduce in a fairly round ball shape.
They occur primarily in reproductive age women and
grow in size if estrogen and progesterone is present
and do not increase in size if estrogen and progesterone
levels are low . Birth
control pills play a role in stimulating fibroid
growth and the fibroids may regress in size when the
pills are stopped . We used to think that it was just
the estrogen component that was necessary for growth
but it now appears the progesterone is critical to
fibroid growth .
Fibroids are composed of uterine smooth muscle cells
that are "monoclonal", i.e., all of the
muscle cells in a fibroid are descendents of one cell
that has just gone haywire . Beyond that, we don't
know if the initial stimulus is from genetics, a virus,
inflammatory repair of normal cell loss or any other
of numerous possible causes.
Do fibroids go away after menopause?
In general, yes. Fibroids
decrease in size to a very small size after menopause
if a woman does not take estrogen replacement. They
do not totally go away; there is always a small nucleus
of the fibroid that can become stimulated again under
certain hormonal conditions. For the most part, however,
a woman herself is not aware of them, the doctors
cannot feel the fibroid(s) on pelvic exam and most
of the time, they are below the resolution of ultrasound
by several years after menopause as long as there
is no extra estrogen.
Do estrogens stimulate the growth of fibroids?
After menopause,
taking estrogen and progestin replacement therapy
can cause fibroids to grow . It appears that the progesterone/progestin
component is needed because that is the hormone that
increases cell reproduction (mitotic activity) in
the fibroid itself . We really do not know how much
fibroid growth will be caused by estrogen given alone
without progestin. If you give progestin alone as
add back therapy to women treated with LHRF, the fibroids
will return to pretreatment size , thus illustrating
that it is the progestin more so than the estrogen
that makes fibroids get larger.
Not all estrogens
will stimulate growth, however. In a study using the
anti-estrogen effect of LHRF (Depo-Lupron®) and
giving estriol (a weak estrogen) add back therapy,
it did not reverse the uterine muscle and fibroid
shrinkage from the LHRF (9). In another study using
conjugated estrogens as the estrogen replacement component
after menopause, there was no significant growth of
smaller, asymptomatic fibroids as compared to an almost
identical study that used ethinyl estradiol as the
replacement estrogen (11). When transdermal estradiol
is given Postmenopausal, there is stimulation of uterine
size and fibroid growth (12) and if transdermal estradiol
is compared to conjugated estrogens for HRT, the estradiol
increases the size of uterine fibroids whereas conjugated
estrogens given orally do not (13).
The above data may indicate that for hormone replacement
therapy in the presence of fibroids, it is better
to use conjugated estrogens (predominantly estrone)
or estriol rather than synthetic ethinyl estradiol
(used mostly in oral contraceptives) or naturally
occurring estradiol.
Does stopping estrogens or taking an anti
estrogen medicine make fibroids get smaller or go
away?
We know that premenopausal, treatment with the anti-estrogen
LHRF causes the uterus and fibroids to shrink about
35-50% (14, 15). There is not much experience yet
with the selective estrogen receptor modulator, raloxifene
(Evista®), which has an anti estrogen effect on
endometrial growth, but in animal models, it acts
as an anti-estrogen on uterine smooth muscle (16)
and it appears it may be capable of shrinking fibroids
even though estrogen is still present (17).
Based on the above data, if you were premenopausal
and had large fibroids causing pressure symptoms but
not abnormal bleeding, it might be worth asking your
doctor to consider giving you raloxifene to see if
it shrinks the fibroids. If you are postmenopausal
and hormone replacement therapy causes fibroids to
get bigger, you could ask your doctor to similarly
consider the simultaneous administration of raloxifene.
Therapy such as that would be somewhat experimental
so it needs to be done under a doctor's supervision.
Do you get bleeding after discontinuing estrogen
replacement therapy?
When you discontinue any hormone replacement therapy,
there may be menstrual bleeding especially if a woman
is close to the menopause. The further removed from
menopause, the less likely there is that uterine endometrial
tissue is present in enough amount to cause a menses.
If bleeding does take place, it usually last less
than a week although occasionally spotting can continue
for 2-3 weeks. After that, there should be no more
vaginal bleeding if a woman is truly menopausal.
Occasionally perimenopausal women are placed on hormone
replacement therapy or even low dose birth control
pills to control bleeding problems or intermittent
hot flashes and other perimenopausal
mood symptoms. When hormone replacement therapy is
discontinued under these circumstances, either regular
menses or irregular abnormal bleeding may return.
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