I have excessive hair growth on my stomach below belly button (a girl). why other girls don't have it?

Hirsutism: Excessive hair growth in the midline that is coarse dark and pigmented is called hirsutism and it indicates increased level of male hormone. It require evaluation to determine its truly hirsutism and what is the source of increased androgen: the ovary, the adrenal gland or somewhere else. Sometimes a tumor in the ovary or adrenal is the cause but mostly benign. Treatment options are available.