During estrus, GnRH from the hypothalamus stimulates the anterior pituitary to produce FSH and LH. First FSH and then LH stimulate the growth of follicles on the ovaries. As the follicles get larger, one follicle gets larger than the rest and it produces both estrogen in response to LH and inhibin in response to FSH. The inhibin feeds back on the anterior pituitary to inhibit the secretion of FSH. This prevents further follicles from developing as FSH levels go down. The estrogen produced from the largest follicle feeds back on the anterior pituitary and hypothalamus to stimulate GnRH and LH secretion which in turn increases estrogen. This positive feedback loop continues until the LH triggers ovulation of the follicle. The estrogen also triggers estrus behavior and an increase in fluid accumulation in the uterine tissue known as edema.