What Causes Fibroids To Grow? Risk/Protective Factors

What Causes Fibroids To Grow? Which Risk Factors Might Predispose a Woman To Develop Uterine Fibroid Tumors? Are There Protective Factors That Might Reduce Fibroid Problems?

Researchers are uncertain exactly what causes fibroids to grow. Most medical professionals accept that each tumor develops from one mutant muscle cell in the uterus. This rogue cell experiences rapid multiplication under the influence of hormones, estrogen in particular. In time the aberrant cells then overproduce large amounts of collagen and other proteins.​ More gene mutations exist in fibroid cells that seem to alter the cell’s growth as well. There may be other environmental causes, yet undetermined, that can further stimulate fibroid growth.

The female hormones, estrogen and progesterone, are necessary for fibroids to grow. The development of a fibroid, though, requires more. An interaction of estrogen, progesterone and cell growth factors seems to form the “perfect storm” for fibroid growth. Fibroids generally do not occur before puberty, when estrogen and progesterone production begins. They most often shrink then after menopause, when hormone production decreases.

Important to note: women with fibroids are not more prone to fibrocystic changes in the breast, an unrelated condition. Neither are they more prone to develop any other benign or cancerous conditions.

While researchers continue to study what causes fibroids, some risk factors are under special scrutiny. Other than being a woman of reproductive age, these factors include obesity, family history, childlessness, early onset of menstrual periods and late menopause. Also important, different factors may be protective against fibroid formation. Diet, exercise, parity and other factors may guard against the development of fibroids. Read further for more details.

Suspected Causes of Fibroids

Doctors do not yet know precisely what causes fibroids. Research and clinical experience, though, point to the following influences as being operative:

What Causes Fibroids: Genetic Changes/Family History

Tissue samples from many fibroids contain evidence of certain genetic changes. These alterations make them different from the genes found in normal uterine muscle cells. It appears that at least some of these changes can pass down through family generations. There is evidence that certain fibroids do run in families. For example if one identical twin has fibroids, her twin sister is more likely to have fibroids than are two nonidentical twins or two non-twin sisters. Women whose mothers or sisters have/had fibroids are at higher risk of developing them too. Research shows that if a mother has a history of fibroids, then her daughter is three times more likely to have fibroids than someone without the genetic ties.

What Causes Fibroids: Reproductive History

Pregnancy increases the production of both estrogen and progesterone in a woman’s body. Fibroids more often develop and grow fast while a woman is pregnant. The first 12 or 13 weeks of pregnancy is prime time for fibroid development. Such fibroids, though, often shrink or even disappear on their own after the woman gives birth.

What Causes Fibroids: Hormones

Estrogen and progesterone are two of the hormones produced by a woman’s ovaries. Fibroid tissue contains more estrogen and progesterone receptors than normal uterine muscle cells do. Surges of estrogen and progesterone stimulate development and regeneration of the uterine lining. This action occurs during each monthly menstrual cycle in preparation for pregnancy. The two hormones also appear to promote the growth of fibroids.

Fibroids often grow faster during the first trimester of pregnancy, when hormone levels are high. Sometimes they then shrink after the birth, when hormone production levels off. The use of anti-hormone medication may also cause fibroids to shrink. Research shows, too, that many times fibroids diminish once a woman’s body reaches menopause. At that point hormone production decreases, and fibroids may disappear all on their own.

Levels of estrogen and progesterone in a fibroid sufferer’s blood are almost always normal. Contrary to expectation, women with fibroids are not making too much estrogen or progesterone. Instead, research shows that fibroids themselves contain certain specific enzymes. These enzymes can convert androgens (hormones made by the ovary and the adrenal gland) into estrogens within the fibroid. In this way, then, fibroid cells actually do contain higher levels of estrogen than the rest of the body.

Fibroids are also sensitive to the progesterone hormone.  They appear to thrive during the time of a woman’s menstrual cycle when progesterone levels are highest.

What Causes Fibroids: Other Growth Factors

Other substances that help the body maintain tissues may also speed up fibroid growth. One example is insulin-like growth factor. Other special proteins (e.g., TGF-B, bFGF, EGF, PDGF and VEGF) can also appear in a fibroid sufferer’s bloodstream.  These substances, too, seem to stimulate fibroid development. Some growth factors encourage fibroid cell growth. Others encourage blood vessel growth to feed the fibroids. Researchers are continuing to study the role of these proteins for significance.

 Risk Factors for Developing Uterine Fibroids

Some circumstances appear to have a disproportionate impact on fibroid development. Various risk factors are currently under study to evaluate their effect on formation and growth of uterine fibroid tumors.

Possibly Protective Factors

Research studies suggest, too, that certain protective factors may offer some safety against developing fibroids. The exact role and mechanism for such factors is still speculative and needs further study.

Going Forward — Looking for Treatment Methods

Although researchers continue to study the causes of fibroids, there is only limited data about prevention. Fortunately, though, just a small percentage of uterine fibroid tumors ever need intervention. Depending on the details of a woman’s condition, a variety of treatment methods may be available.