Follicular phase

Progesterone is the hormone we all know and love. Progesterone is a sex hormone that is produced primarily in the ovaries. It helps thicken the uterine lining so a fertilized egg can implant in the uterus. In the first part of the menstrual cycle, the follicular phase, progesterone levels are low. Luteinizing hormone stimulates the release of an egg and after ovulation occurs progesterone levels begin to increase