Are there different phases to a menstrual cycle?
A. Yes, the menstrual cycle can be divided into three phases: the follicular (proliferative) phase the ovulatory phase the luteal (secretory) phase The follicular phase begins with the first day of menses (menstrual flow) and continues to approximately day 13 or 14 when ovulation takes place. During the follicular phase, FSH and LH are slowly rising in preparation for the LH surge (very high level of LH) at the time of ovulation. FSH is stimulating the growth of follicles in the ovary. Estrogen and progesterone are relatively low throughout this time but slowly begin to rise toward the end of this phase. Estrogen, and progesterone to a lesser degree, are steroid hormones produced by cells of the developing ovarian follicle. Estrogen causes the endometrium to increase in thickness and vascularization (i.e.blood supply). At the end of the proliferative (follicular) phase, the endometrium is 2-3 mm thick and the glands are straight tubules with narrow lumens.
