According to the medical textbook "Williams Gynecology," uterine fibroids (also called leiomyomas) are benign, estrogen-sensitive tumors that originate from the smooth muscle layer of the uterus (the myometrium). They are often referred to as fibroids because they have a fibrous texture because of an abundance of collagen. Uterine fibroids are round, pearly, firm and rubbery in appearance, and an affected woman generally has six to seven tumors of varying size in her uterus.
Incidence of Fibroids
According to Dr. Vern L. Katz, author of "Comprehensive Gynecology," the incidence of symptomatic uterine fibroids is said to be 30 percent to 50 percent of perimenopausal women, but microscopic and sonographic studies have shown incidence as high as 70 to 80 percent. During the reproductive years, the incidence increases with age and is more common in African American women than Caucasian, Hispanic or Asian women. Additionally, studies have shown that there is a greater risk of developing fibroids in women who have a family history of the condition. In many women, uterine fibroids are asymptomatic. However, they may manifest in many different ways depending upon the size, amount and location of the masses.
Estrogen and Fibroids
Uterine fibroids are estrogen- and progesterone-sensitive masses, according to the authors of "Williams Gynecology." The mass itself creates an estrogenic surrounding, which seems to aid its growth. Thus, hyperestrogenic states favor growth of uterine fibroids. Increased body-mass index is associated with fibroid development because fat tissue produces estrogen. In addition, early menarche (first menstrual period) imposes a greater risk of fibroid development because it allows for a longer duration of estrogen exposure. On the other hand, it has been found that women who smoke cigarettes have a reduced risk of uterine fibroids because cigarette smoking changes the manner in which estrogen is processed in the body and causes lower circulating levels of active estrogen.
In premenopausal women, estrogen and progesterone therapy has not been shown to induce fibroid formation and oral contraceptives lower or do not change the risk of development. In menopausal women, hormone replacement therapy has been shown to stimulate growth of fibroids or cause no change.
Progesterone and Fibroids
According to "Williams Gynecology," the role of progesterone has not been fully made clear, but during states of progesterone dominance, fibroid growth is shown to be less vigorous. Thus, pregnancy is an interval in which fibroid growth should theoretically be suspended. This is supported by studies demonstrating lower rates of fibroid development in women who give birth at an early age, women who have more children, and women with a recent pregnancy.
Symptoms
Most women with uterine fibroids are asymptomatic. However, symptomatic patients typically experience bleeding, pain, pressure and/or infertility. Generally, larger fibroids are more likely to cause symptoms. The most common symptom is abnormally heavy and prolonged menstrual periods. However, a uterus that is enlarged enough can cause pressure, urinary frequency or incontinence and constipation.
Diagnosis
Uterine fibroids are diagnosed by pelvic examination, which shows enlargement and/or an irregularly shaped uterus. Ultrasound and other imaging modalities can also be used to identify fibroids.
References
- "Williams Gynecology, Ch. 9"; John O. Schorge MD, Joseph I. Schaffer MD, Lisa M. Halvorson MD, Barbara L. Hoffman MD, Karen D. Bradshaw MD, F. Gary Cunningham MD; 2008
- "Comprehensive Gynecology, Ch. 18,"; Vern L. Katz MD; 2007
