Women who have high levels of both testosterone and estrogen in midlife may face a greater risk of developing benign tumors on the uterus called uterine fibroids than women with low levels of the hormones.

Three out of four women develop uterine fibroids by age 50, and fibroids can contribute to irregular bleeding, infertility, pelvic pain, recurrent pregnancy loss and other reproductive complications. The first-line treatment is undergoing a hysterectomy, and there are few other treatment options currently available.

Scientists at the Stanford University School of Medicine (Stanford, CA, USA) and their colleagues examined hormone levels and the incidence of uterine fibroids in women participating in the Study of Women's Health around the Nation (SWAN). Among the 3,240 women enrolled at the beginning of the study, 43.6% completed the follow-up visits. During nearly annual visits, participants had their blood tested for estrogen and androgen levels. In addition, the women were asked whether they had been diagnosed with or treated for uterine fibroids.

Endocrine assays were performed with an Automated Chemiluminescence System (ACS)-180 analyzer (Bayer Diagnostics Corporation, Pittsburgh, PA, USA) using a double-antibody chemiluminescent immunoassay with a solid phase anti-IgG immunoglobulin conjugated to paramagnetic particles, anti-ligand antibody, and competitive ligand labeled with dimethyl acridinium ester. The bioactive form of estrogen (17β-estradiol [E2]) was assessed with a modified the rabbit anti-E2-6 ACS-180 immunoassay to increase sensitivity and had a lower limit of detection of 1.0 pg/mL. Bioavailable testosterone (T) was measured using a modified rabbit polyclonal anti-T ACS-180 immunoassay.

Among the participants, 512 women reported having a single incidence of fibroids, and an additional 478 women had recurrent cases. Participants who had high levels of testosterone in the blood were 1.33 times more likely to develop a single incidence of fibroids than women who had low levels of testosterone. Women who had high levels of testosterone and estrogen faced an even greater risk. Although women with high levels of both hormones were more likely to report a single incidence of fibroids, they also were less likely to have a recurrence than women with low levels of the hormones.

Jennifer S. Lee, MD, PhD, a senior author of the study, said, “Our findings are particularly interesting because testosterone was previously unrecognized as a factor in the development of uterine fibroids. The study opens up new lines of inquiry regarding how fibroids develop and how they are treated. Given that managing uterine fibroids costs an estimated USD 34.4 billion in annual medical expenditures nationwide, it is important to identify new ways to better treat this common condition. The study was published on December 15, 2015 in the Journal of Clinical Endocrinology & Metabolism.

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Stanford University School of Medicine 
Bayer Diagnostics Corporation