Final answer:
Estrogen levels significantly influence the ovarian and menstrual cycles: low levels signal the start of the follicular phase and endometrial maintenance for pregnancy; elevated estrogen levels trigger ovulation, facilitate sperm viability, and prepare the uterus for potential implantation. During peri-menopause, fluctuating estrogen and decreased progesterone can result in various physical symptoms and increase the risk of endometrial issues.
Step-by-step explanation:
During the ovarian cycle, estrogen plays a crucial role in the regulatory changes that occur within the female reproductive system. When estrogen levels are low, at the beginning of the follicular phase, follicles on the ovary surface mature, preparing the egg for eventual ovulation. Estrogens and a low level of progesterone released by these follicles maintain the endometrium for potential pregnancy.
As estrogen levels rise and reach their peak, there is a switch from negative feedback to positive feedback, which stimulates the LH surge and triggers ovulation around day 14 of a typical 28-day cycle. High levels of estrogen increase uterine tube contractions for the transport of the ovulated oocyte and decrease vaginal acidity, making the environment more favorable for sperm. They also prompt the corpus luteum formation, which secretes progesterone for the secretory phase of the uterine cycle, preparing the endometrium for potential implantation.
In contrast, low levels of estrogen during peri-menopause can lead to conditions like uterine fibroids, irregular bleeding, hot flashes, night sweats, and changes in mood. Reduced progesterone levels during this phase lead to an increased risk of endometrial hyperplasia and possibly endometrial cancer.