Effects of estrogen monotherapy on breast tissue in the primate model (Macaca fascicularis)

Much is unknown about the effects of estrogen's on the mammary gland in postmenopausal women today. In a recent study of estrogenmonotherapy 28 adult, surgically postmenopausal female monkeys (Macaca fascicularis) were treated continuously with estradiol or were given only a diet (control group). After 6 months serum levels of estradiol and progesterone, morphometrical, histopathological and immunohistochemical measurements of the mammary gland were performed. In monkeys receiving estradiol the mammary epithel thickness and the mammary epithelial area (as percentage of total breast area) increased. Estradiol induced mammary gland hyperplasia, but we did not see any atypical hyperplasia. Estradiol and progesterone receptors staining in mammary ducts and lobuli increased (not significant). Estradiol induced a mammary gland proliferation (not significant) shown as increased staining for PCNA and Ki67.