How Will Taking ERT Affect Fibroids?
Frederick R. Jelovsek MD, MS
"If you have been on ERT and have a fibroid, what will happen if you stop the ERT? Will you begin to bleed, will the fibroid shrink?" Anon
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 (1). Birth control pills play a role in stimulating fibroid growth and the fibroids may regress in size when the pills are stopped (2). 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 (3).
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 (4). 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 (5). It appears that the progesterone/progestin component is needed because that is the hormone that increases cell reproduction (mitotic activity) in the fibroid itself (6). 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 (7, 8), 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 (10) 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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