Answer
Estrogen and progesterone prepare the endometrium for pregnancy --implantation of the ovum after ovulation. As the endometrium grows, its endometrial glands produce glycogen to sustain/nourish the egg -- if it is implanted. After implantation, the developing embryo secretes progesterone ( also secreted by placenta and adrenals): this hormone helps to maintain the egg/embryo in place and promotes development of mammary glands.
Work Step by Step
Progesterone, through a negative feedback loop effect, also inhibits the secretion of gonadotropin releasing hormone (GnRH); as a consequence, there is no new ovarian cycle.
