Event marking the begining of menstural cycle

Question

Specify the event which marks the beginning of menstrual cycle? Explain the concentration of blood of FSH, LH, estrogens and progesterone during this phase of cycle?

Answer 1

By convention, menstrual cycle begins at the day where menses begins. Menses refers to the endometrial hemorrhage secreted through the vaginal canal. At these days hormones FSH, LH, estrogens and progesterone are generally in low concentration.