Megesterol: a synthetic progestational compound used to treat endometrial carcinoma and an appetite stimulant approved for the treatment of weight loss in people with AIDS. Megestrol acetate is a synthetic version of the female hormone PROGESTERONE. Most of the weight gain it leads to has been found to be fat rather than PROTEIN. Possible SIDE EFFECTS include HYPERGLYCEMIA, occasional impotence and decreased LIBIDO in men and uterine bleeding in women.