What are they? What causes them to grow?

What are Uterine Fibroids?

The walls of the uterus are made of smooth muscle called myometrium, and the inside lining, with glandular tissue, is called endometrium.  “Uterine fibroid” is a slang term for leiomyoma, or often simply  myoma. Fibroids are benign tumors made of smooth muscle cells.

Fibroids are extremely common.  It is often stated that 30% of women have uterine fibroids, but this is an underestimate.  Most women have fibroids, but many are too small to be detected and do not cause any problems.  They are more common in women of African descent, with one study showing an incidence of 60% by the age of 35 and 80% by the age of 50.  In Caucasian women the incidence has been found to be 40% by age 35 and 70% by age 50.

What Causes Uterine Fibroids?

There are a number of factors that cause fibroids.  There is a genetic factor, as the DNA in fibroids frequently show abnormalities.  Likely there is an abnormality in which the cells in fibroid handle estrogen and progesterone.  Fibroids are not caused by too much estrogen any more than fire is caused by too much air!

Can Fibroids turn to Cancer?

There is no evidence that benign fibroids can turn into cancer. One study looked at 371 study in women with rapidly growing myomas and found only one sarcoma (cancer) or 0.26%, in the group.  Although women are often advised to have surgery because of fear of cancer developing in a fibroid, the actual risk is very low.  Although Leiomyosarcomas are serious malignancy, the actual risk of a seemingly benign fibroid being malignant is extremely low.

What Causes Fibroids to Grow?

Fibroids are sensitive to both estrogen and progesterone. Without these hormones most fibroids will shrink but not go away.  Do not interpret this to mean that fibroids are caused by too much estrogen.  That would be the same as saying that too much air causes fires because fires go out without air!  Changes in fibroid cells cause fibroids to be more sensitive to normal levels of estrogen and progesterone.

Do Birth Control Pills Cause Fibroids to Grow?

There is no evidence that birth control pills increase the risk of developing fibroids or causes new fibroids to grow.  There is some evidence, in fact, that certain birth control pills may slow the growth of fibroids.

Editor's Note: This post was picked up from Uterine Fibroids blog: An Expert Speaks Out.The blog posts do not intend to diagnose, treat, or cure any condition and are not a substitute for consultation with a physician. The postings are presented for educational purposes only.