Yes. Female hormones are not at the same level all month long. During the bleeding period, both Estradiol and Progesterone are low. After the typical 5 days of bleeding, the ovaries begin to produce estradiol, which begins to grow the endometrial lining. At day 14 per say, ovulation occurs where Progesterone surges along with Estradiol occurs. This remains for a few days & then goes to low levels.