How does the drug megesterol acetate create an appetite for someone?

im just curious because my doctor put me on this drug and i went from barely eatting to eatting everythiing i see. my doctor said that this drug is a hormone and it stimulates my addrenal cortex. he said he usually prescribes this drug for anorexia, cancer or hiv/aids patients and i am none of those i suffer from extreme anxiety with some depression which causes me to not eat. anyone know about this drug/hormone and how it works and if it reaches a peak and eventually stops working?