Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Cushing disease ?
    ### Response:
    Cushing disease is caused by elevated levels of a hormone called cortisol, which leads to a wide variety of signs and symptoms. This condition usually occurs in adults between the ages of 20 and 50; however, children may also be affected. The first sign of this condition is usually weight gain around the trunk and in the face.
    