Adipose tissue is the primary site of estrogen production in postmenopausal women, according to Medical News Today. Estrogen is mainly produced in the ovaries in women who have not yet reached menopause.
Menopause begins 12 months after a woman has her last period, and the average age at which it occurs in the United States is 51 years, according to Mayo Clinic. Postmenopausal women who have high blood levels of the estrogen estradiol have an increased risk of getting breast cancer, notes the Susan G. Komen foundation. Since estrogen is mainly produced in fat tissue after menopause, higher body weight in postmenopausal women is also linked to an increased risk of breast cancer.