Uterine Fibroids and Hysterectomy - Causes

Causes

Inherited genetic factors may be important in many cases of fibroids. Researchers are investigating unique genetic factors that regulate hormones. Proteins called growth factors may be responsible for some of the abnormalities leading to uterine muscle overgrowth and fibroids. Scientists have identified chromosomes carrying a total of 145 genes that may have an effect on fibroid growth. Some experts report that uterine fibroids are inherited from paternal genes (the father's side).

Female Hormones

Uterine fibroids often grow during pregnancy and they degenerate after menopause. From these observations and certain studies researchers are fairly certain that the female hormones, both estrogen and progesterone, play a role in their growth. Their role, however, is not clear. Some theories about the relationship to fibroids and estrogen include the following:

Estrogen patterns in fibroids are similar to those in pregnancy. That is, like smooth muscle cells in the uterus during pregnancy, fibroid cells exposed to female hormones do not respond normally to signals that would make them self-destruct and return to a nonpregnant state. (This natural self-destruction is a process called apoptosis). Instead, they continue to grow.

Some evidence suggests that estrogen may inhibit a tumor-suppressor gene called p53 in fibroid tissue, therefore triggering cell proliferation leading to fibroid growth. (P53 plays a role in some cancer-cell growth, although in this case the process is not malignant.)

Growth Factors

The formation of fibroids may be attributable to abnormalities in substances called growth factors. These are special proteins secreted by different cell types and are responsible for cell-to-cell interaction. Many of these substances regulate a process called angiogenesis, which causes new blood vessels to sprout from pre-existing ones. The production of new blood vessels then feeds any existing growth, such as fibroids.

The growth factors that appear to play an important role in many female reproductive disorders are Basic Fibroblast Growth Factor (BFGF) and Vascular Endothelial Growth Factor (VEGF). BFGFs are involved in the proliferation of cells that form connective tissue, which supports the body's organs and structure. VEGFs are involved with cell growth in smooth muscles that line blood vessels. There is some evidence that they play role in uterine fibroids.

Other growth factors being studied specifically for fibroids are Insulin-like Growth Factor (IGF)-I, Epidermal Growth Factor (EGF), Platelet Derived Growth Factor, and Transforming Growth Factor (TGF). TGF is proving to have multiple effects that may of particular importance in the development of fibroids.