Used primarily in the treatment of advanced breast and endometrial cancers, megestrol works by altering hormone levels to slow tumor growth. It is also prescribed to manage appetite loss and weight reduction in patients with cancer or HIV/AIDS, helping to improve nutritional intake and quality of life. In veterinary medicine, it is sometimes used to stimulate appetite in cats and dogs. Additionally, megestrol may be used off-label for conditions involving hormonal imbalances or to control certain types of abnormal uterine bleeding.