Uterine Fibroid -

Uterine fibroids are benign tumors that originate in the uterus (womb). It is not known exactly why women develop uterine fibroids. Most women with uterine fibroids have no symptoms. However, fibroids can cause a number of symptoms depending on their size, location within the uterus, and how close they are to adjacent pelvic organs. These are most commonly abnormal bleeding, pain and pressure.

Symptoms -

Many women who have fibroids don't have any symptoms. In those that do, symptoms can be influenced by the location, size and number of fibroids. In women who have symptoms, the most common symptoms of uterine fibroids include:

Heavy menstrual bleeding
Menstrual periods lasting more than a week
Pelvic pressure or pain
Frequent urination
Difficulty emptying the bladder
Constipation
Backache or leg pains

Causes -

Doctors don't know the cause of uterine fibroids, but research and clinical experience point to these factors:
Genetic changes. Many fibroids contain changes in genes that differ from those in normal uterine muscle cells.
Hormones. Estrogen and progesterone, two hormones that stimulate development of the uterine lining during each menstrual cycle in preparation for pregnancy, appear to promote the growth of fibroids. Fibroids contain more estrogen and progesterone receptors than normal uterine muscle cells do. Fibroids tend to shrink after menopause due to a decrease in hormone production.
Other growth factors. Substances that help the body maintain tissues, such as insulin-like growth factor, may affect fibroid growth.