Green line: LH surges and peaks before ovulation Blue line: FSH : responsible for follicular development in the early phase of the cycle, increases gradually upto ovulation Red line: Estrogen : increases steadily in follicular phase secondary to follicular development as estrogen is produced by the follicle and is responsible for growth of the endometrium in follicular phase Dotted line (marked X ): Progesterone: stas to rise after ovulation (after formation of corpus luteum), responsible for stabilisation of endometrium. Withdrawl of progesterone leads to endometrial shedding (menstrual bleed)