Estrogens
secreted by theca interna and granulosa cells of ovarian follicles, corpus luteum and placenta under pituitary gonadotropins
1. Phase - FSH ( early maturation of ovarian follicle, stimulation of estrogens secretion)
2. Phase - LH (ovulation, formation of corpus luteum, stimulation of estrogen and progesterone secretion from corpus luteum
biosynthesis from androgens by aromatization of testosterone and androstenedione by aromatase in circulation