Peter Attia· MD
The cycle is divided into two phases technically three because there's a menstrual phase here but let's just acknowledge that the menstrual phase which starts at day zero that's the first day of bleeding even if it's just spotting and it's not a heavy period That's day zero that's the shedding of the endometrial lining which we'll talk about then you move into a follicular phase and the purpose of that phase which is really driven by follicle stimulating hormone estrogen is to ripen the follicle for ovulation ovulation takes place mid-cycle after ovulation we move into the luteal phase the luteal phase is dominated by luteinizing hormone and progesterone and the purpose of the luteal phase is to prepare the endometrial lining for implantation