Ladies,

Did you ever want to know the morphogenesis (or morphology) of breast tissue during a menstrual cycle?.....well here yah go. I've found increasing evidence (and not just this study) that progesterone and estrogen during luteal stage produced a 34 fold increase in breast tissue.

Morphological Changes in Breast Tissue with Menstrual Cycle

we found increased mitotic activity in the breast lobules in the luteal phase. Only on rare occasion was a mitotic figure, most likely persistent from the previous cycle, observed in the early follicular phase. This morphologic finding has been confirmed by studies that have compared the tritiated thymidine labeling indices in the follicular and luteal phases (26). The cumulative effect of high levels of estrogen and progesterone that occurs in the late luteal phase (21, 27) seems to be necessary to induce proliferation in breast epithelial cells. The proliferative activity appeared confined to the luminal epithelial cells. This finding is supported by experimental data (9, 28) that suggest that luminal cells can give rise to both luminal and myoepithelial cells. The breast epithelium, unlike the endometrium, cannot be shed at the end of the cycle; regression at the end of the cycle is by apoptosis. The apoptotic figures are plentiful toward the late luteal phase of the cycle (Stage 4). These findings have been previously described and are supported by quantitative assessments of apoptosis (21, 22).
http://www.nature.com/modpathol/journal/v15/n12/pdf/3880699a.pdf

Happy Growing,