Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Secondary adrenal insufficiency ?
    ### Response:
    Adrenal insufficiency is an endocrine disorder that occurs when the adrenal glands do not produce enough of certain hormones. Secondary adrenal insufficiency occurs when the pituitary gland (a pea-sized gland at the base of the brain) fails to produce enough adrenocorticotropin (ACTH), a hormone that stimulates the adrenal glands to produce the hormone cortisol.
    