Final answer:
During proestrus, GnRH levels are increasing to stimulate the production of FSH and LH, which in turn promotes the growth of ovarian follicles and the production of estrogen.
Step-by-step explanation:
During proestrus, the levels of Gonadotropin-releasing hormone (GnRH) will be increasing. This occurs as part of the reproductive cycle to stimulate the anterior pituitary gland to secrete Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH). FSH and LH then promote the growth of follicles on the ovary, leading to increased production of estrogen. Eventually, the rise in estrogen levels leads to a positive feedback effect on GnRH, further increasing its levels during proestrus.
However, this process can be influenced by other hormones such as progesterone and estrogen, which may lead to the fluctuation of GnRH depending on various stages of the reproductive cycle. For example, Secretion of GnRH by the hypothalamus is inhibited by low levels of estradiol but stimulated by high levels of estradiol. This reflects the complex interplay between hormones that regulate the reproductive cycle.