Amenorrhea means no menstruation. It’s normally before puberty, during pregnancy and lactation and after menopause. Sometimes though menstruation either never starts which is called primary amenorrhea or suddenly stops in a person who's previously menstruating which is called secondary amenorrhea . The menstrual cycle as a whole are controlled by the hypothalamus and the pituitary gland all the way up in the brain. The hypothalamus secretes gonadotropin releasing hormone or GnRH which makes the nearby anterior pituitary gland release follicle stimulating hormone or FSH and luteinizing hormone or LH in the first two weeks of an average 28-day cycle. The ovaries go through the follicular phase meaning that out of the many follicles scattered throughout the ovaries a couple of them enter a race to become the dominant follicle that will be released at ovulation. All the developing follicles secrete loads of oestrogen which negatively inhibits pituitary FSH. In the meantime the ute...