Etiology of Uterine Fibroids Still Largely a Mystery.

More research is needed into the etiology of uterine fibroids, including studies that clarify the role of estrogen and progesterone and that identify risk factors, according to a literature review led by a School of Public Health researcher.

Writing in the journal Clinical Obstetrics and Gynecology, Lauren Wise, professor of epidemiology, and co-author Shannon Laughlin-Tommaso of the Department of Obstetrics and Gynecology at the Mayo Clinic, review published studies and call for further research into the causes of uterine fibroids to help guide prevention strategies.

While uterine fibroids are benign growths and often asymptomatic, they also can cause excessive menstrual bleeding, pelvic pain, infertility, and other symptoms that adversely affect a woman’s quality of life. They account for nearly 40 percent of all hysterectomies among women 18 to 44 years old, at an estimated $9.4 billion in annual health care costs.

According to Wise and Laughlin-Tommaso, studies have found that rates of fibroids tend to increase with age through the reproductive years and decline after menopause. Fibroids are two to three times more common among black women than white women, yet identified risk factors have not been able to explain this racial disparity.

“Uterine fibroids are the most common diagnosis among inpatient hospitalizations for gynecologic conditions of women in childbearing years, and they disproportionately affect black women. Greater research is needed about why they grow and how to prevent them,” says Wise. She said there have been relatively few studies “identifying opportunities for primary prevention.”

Past studies have indicated that fibroid risk increases with earlier onset of menarche and decreases among women who have given birth (particularly a recent birth). Use of progestin-only injectable contraceptives is associated with reduced risk. Other research has found modest positive associations between alcohol intake and fibroid incidence, as well as early life abuse, stress, and overweight/obesity. Several studies have found evidence of a genetic predisposition to fibroids.

Wise and Laughlin-Tommaso say that while estrogen and progesterone are “almost certainly involved” in fibroid growth, the mechanisms through which they act are not well understood.

They call for more research into nutritional and psychosocial factors, reproductive tract infections, and environmental toxicants that can mimic the effects of sex steroid hormones or bind to their receptors (e.g. phthalates).

Preliminary studies examining vitamin D deficiency as a risk factor have yielded consistent positive associations. If confirmed in prospective cohort studies, vitamin D deficiency—which is more common among black women than white women—could explain a large fraction of the black-white disparity in rates, Wise and Laughlin-Tommaso say.

The authors also urge future studies that look at the factors influencing treatment choices, such as hysterectomy.

“Studies should attempt to determine the extent to which patient characteristics, ultrasonographic features and physiological measures are related to fibroid progression from clinical diagnosis (to surgery),” they write.

—Lisa Chedekel