FSH, LH, Oestrogen
Menstrual cycle in humans is controlled by several endocrine hormones. In the beginning of the cycle, FSH (follicle stimulating hormone), secreted by the pituitary, initiates the development of an ovarian follicle. A growing ovarian follicle gradually secretes increasing amounts of estrogen. This, in turn, leads to a sudden surge of LH secretion by the pituitary. As the LH (luteinizing hormone) level in blood suddenly increases, there is ovulation. After ovulation, the ruptured follicle is converted to a structure called corpus luteum, which secretes mainly progesterone. Progesterone prepares the uterus for a possible pregnancy. If there is no fertilisation progesterone level falls and there is beginning of a new cycle.