Absence of ovulation caused by insufficient GnRH drive from the hypothalamus, so that the pituitary gland doesn't produce enough follicle stimulating hormone. Usually accompanied by absent periods (amenorrhea).

"Anorexia" means a profound loss of appetite, followed by loss of weight; "nervosa" means that there is a nervous or mental basis for the state, in this case a belief by the person affected, and contrary to the perception of others, that she (very rarely he) is overweight. She stops eating, may induce vomiting, and uses laxatives to keep the intestines empty and the stomach flat. The menstrual periods stop (there is amenorrhea for two reasons: the weight loss and the underlying mental disturbance, both of which cause hypothalamic anovulation. Medical complications from induced vomiting and laxative abuse can be serious, occasionally fatal. Treatment, which includes psychological and psychiatric counseling, is difficult and is not always completely accomplished. It's a condition chiefly of adolescent girls; the younger the patient the better the chance of cure. For fertility, ovulation induction as often required.