Final answer:
Physiologic leukorrhea is a normal vaginal discharge appearing before menses, which marks the shedding of the endometrial lining. It may increase as estrogen levels rise during the proliferative phase before ovulation.
Step-by-step explanation:
Physiologic leukorrhea is a normal vaginal discharge that occurs as part of the menstrual cycle. It typically starts prior to menses or the onset of menstruation. The menstrual cycle has three main phases: the menses phase, the proliferative phase, and the secretory phase. The menses phase is marked by the shedding of the endometrial lining when levels of progesterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) are low. This phase corresponds with the early days of the follicular phase of the ovarian cycle and occurs after the corpus luteum degrades into the corpus albicans if no pregnancy occurs, leading to a decrease in estrogen and progesterone levels, eventually resulting in menstruation.
Just before this phase, there may be a change in vaginal discharge, which can indicate the upcoming shedding of the endometrium. While the exact timing can vary among individuals, normal vaginal discharge or leukorrhea that occurs before menstruation is usually clear to white, thin to thick, and may increase in abundance as estrogen levels rise during the proliferative phase leading up to ovulation.