Final answer:
The hypothalamus senses low hormone levels and secretes GnRH in the female reproductive system.
Step-by-step explanation:
In the female reproductive system, the hypothalamus senses low hormone levels and secretes GnRH (gonadotropin-releasing hormone).
The secretion of GnRH by the hypothalamus is inhibited by low levels of estradiol (a type of estrogen hormone) and stimulated by high levels of estradiol. Estradiol is produced in the ovaries and is involved in regulating the menstrual cycle.
GnRH stimulates the production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which play important roles in the female reproductive system.