What are the causes of amenorhea?

Many: Amenorrhea has many causes. Many relate to a deficiency in those hormones from the pituitary gland which stimulate the ovaries (gonadotropins) or an excess of another pituitary hormone, prolactin. This might be from a tumor, a loss of pituitary blood supply, trauma, etc. Or as an aging change (menopause). There are less common local ovarian diseases.