The factors that initiate fibroid growth are not known. The vast majority of fibroids occur in women of reproductive age, and according to some estimates, they are diagnosed in African American women two to three times more frequently than in white women. Estrogen often affects the growth of fibroids. Many fibroids are discovered during pregnancy, because they tend to become larger as pregnancy causes an increase in estrogen. Conversely, as estrogen production tapers off during menopause, fibroids may shrink or even disappear.
They are seldom seen in young women who have not begun menstruation and they usually stabilize or regress in women who have passed menopause.
Dependent on the location, there are three types of fibroid development within the uterus. They are as follow:
Intramural fibroids - Typically found inside the uterus lining, these fibroids are the most common. They increase the size of the uterus, cause heavy menstruation and pelvic and back pain.
Submucosal fibroids - Located under the uterus lining, these fibroids can cause heavy bleeding and severe abdominal pain. Although this type is very infrequent, many women suffer from chronic blood loss and develop anemia.
Uterine Fibroids are nodules of smooth muscle cells and fibrous connective tissue that develop within the wall of the uterus. Medically they are called uterine leiomyomata. Fibroids may grow as a single nodule or in clusters and may range in size from 1 mm to more than 20 cm in diameter. They may grow within the wall of the uterus or they may project into the interior cavity or toward the outer surface of the uterus. These overgrowths of uterine tissue are rarely cancerous.
Subserosal fibroids - These fibroids are located near the outside lining of the uterus. Typical symptoms include pelvic pain, back pain and frequent urination. These particular fibroids can develop a stem-like base, thus making them appear to be on a stalk or pedunculated.