Final answer:
The steepest declines in estrogen and progesterone levels occur during peri-menopause when menstrual cycles become irregular. This can lead to hormone-related issues like endometrial hyperplasia, hot flashes, and potentially serious long-term health conditions like osteoporosis and cardiovascular disease.
Step-by-step explanation:
The declines in estrogen and progesterone levels are steepest during the menopausal transition, a phase commonly known as peri-menopause. At this stage, a woman's menstrual cycle becomes irregular, signaling the beginning of the end of reproductive capacity.
Although estrogen levels might be nearly the same as before, progesterone production by the corpus luteum is notably reduced. This hormonal shift can cause endometrial hyperplasia, posing a risk for endometrial cancer. Symptoms like hot flashes, night sweats, and vaginal dryness are also associated with these changes in hormone levels.
Eventually, when a woman reaches menopause, the production of estrogen falls off dramatically due to the depletion of follicles in the ovaries. The post-menopausal period is marked by very low levels of estrogens and progesterone, which can lead to osteoporosis due to decreased bone density and an increased prevalence of cardiovascular disease related to changes in blood cholesterol levels.