This document discusses different types of amenorrhea, or absent menstrual periods. It describes primary amenorrhea, which is the absence of menstruation by age 16 with no development of secondary sex characteristics. This can be caused by hypogonadotropic or hypergonadotropic hypogonadism. Hypergonadotropic amenorrhea is often due to genetic conditions like Turner's syndrome or enzyme deficiencies. Hypogonadotropic amenorrhea has causes like Kallmann's syndrome, infections, or pituitary tumors. Treatment depends on the underlying cause and may include hormone replacement, surgery, or removal of obstructions. Anorexia nervosa can also cause amenorrhea due to severe weight loss and altered