Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Pituitary Tumors ?
    ### Response:
    The pituitary is a small, bean-sized gland that is below the hypothalamus, a structure at the base of the brain, by a thread-like stalk that contains both blood vessels and nerves. It controls a system of hormones in the body that regulate growth, metabolism, the stress response, and functions of the sex organs via the thyroid gland, adrenal gland, ovaries, and testes.
    