Between 80 and 90 percent of ovarian cancers originate in epithelial cells that cover the female reproductive glands, or ovaries. The National Cancer Institute reported the estimated cases of ovarian cancer in 2010 in the United States is 21,880 and the estimated deaths attributable to ovarian cancer is 13,850. Women who have had more than one child, have used oral hormonal contraceptives or have had a tubal ligation have a decreased risk of ovarian cancer. Fertility, age, genetics, hormones, obesity, diets low in fruits and vegetables, smoking and endometrial inflammation contribute to the development of ovarian cancer. Several hormones have been proposed to affect ovarian cancer cell growth. They are gonadotropins, androgens, estrogen, progesterone and insulin-like growth factor.
Gonadotropins
Leutinizing hormone and follicle-stimulating hormone are the gonadotropins released by the pituitary gland. These hormones stimulate the ovaries to produce estrogen and progesterone and trigger ovulation. They also increase the growth of ovarian epithelial cells, a fact that led researchers to propose that gonadotropins contribute to the development of ovarian cancers. Other evidence that supported this hypothesis is that pregnancy and oral contraceptive use, which suppress gonadotropin levels, significantly decrease the risk of ovarian cancer. However, a review study in “Cancer Epidemiology, Biomarkers and Prevention” noted that neither the elevation nor suppression of gonadotropins completely correlates with the risk of ovarian cancer and gonadotropins may not have a direct role in the mechanism by which ovarian cancer develops.
Estrogen and Progesterone
Some studies have demonstrated that estrogen therapy in post-menopausal women increases the risk of ovarian cancer. A study conducted in Denmark on 910,000 women concluded that both estrogen therapy and estrogen in combination with progestin therapy increase the risk of ovarian cancer. However, only 5 percent of ovarian cancers in this study may have been attributable to hormone replacement therapies. Other evidence to support that elevated estrogen levels play a role in ovarian cancer development comes from research that shows oral contraceptive use, which reduces estrogen levels, also prevents ovarian cancer. A study published in “Annals of Oncology” reported that the risk of ovarian cancer was reduced by 50 percent in women who used oral contraceptives for five years or longer. In contrast to estrogen, the review in “Cancer Epidemiology, Biomarkers and Prevention” stated that progesterone levels are most often inversely correlated to ovarian cancer risk.
Androgens
Oral contraceptive use, which substantially decreases the risk of ovarian cancer and also suppresses circulating androgen levels, is the best epidemiologic evidence to support that excess androgens play a role in the development of ovarian cancer. However, the studies that support a direct link between androgens and ovarian cancer are inconclusive. A study published in the journal “Endocrine-Related Cancer” concluded that women who have used testosterone supplements have an increased risk for developing ovarian cancer; however, neither androgen-excess disorders, such as polycystic ovarian syndrome or the androgen medication, Danazol influenced the risk of ovarian cancer in a large population of women. The review in “Cancer Epidemiology, Biomarkers and Prevention” made the conclusion that androgen levels do not correlate with ovarian cancer in older women, but may possibly contribute to alterations in ovarian epithelial cell growth during a woman’s reproductive years.
Insulin-like Growth Factor
There is insufficient research to conclude insulin-like growth factor, also known as IGF-1 contributes to the development of ovarian cancer. A study published in the “International Journal of Cancer” did find that high levels of IGF-1 were observed in persons aged less than 55 with ovarian cancer, but there was not an association between IGF-1 and ovarian cancer risk in the entire study group. These results suggest an increase in circulating levels of IGF-1 is not predictive of ovarian cancer risk.
References
- National Cancer Institute: Ovarian Cancer
- National Cancer Institute: Risk of Ovarian Cancer from Hormone Therapy Confirmed
- “Annals of Oncology”; Reproductive and Hormonal Factors and Ovarian Cancer
- “Endocrine-Related Cancer”; Epithelial Ovarian Cancer
- “Cancer, Epidemiology, Biomarkers and Prevention”; Endogenous Hormones and Ovarian Cancer
