Plasma prolactin and gonadotrophins in anorexia nervosa and amenorrhoea due to weight loss

: The role of prolactin in anorexia nervosa is controversial and both hyperprolactinaemia and normoprolactinaemia were reported in patients with anorexia nervosa. We have measured immunoreactive prolactin by radioimmunoassay in plasma samples from 14 consecutive patients with anorexia nervosa and found normoprolactinaemia in 13 patients and a borderline elevation of plasma prolactin in one patient. The mean plasma prolactin level in anorexia nervosa patients did not differ from an age-matched control group of patients with amenorrhoea due to simple weight loss. While we were unable to confirm reports on the common occurrence of hyperprolactinaemia in anorexia nervosa, the absence of hyperprolactinaemia suggests a different mechanism of amenorrhoea in patients with anorexia nervosa and due to simple dieting from that in idiopathic secondary amenorrhoea in which the frequency of hyperprolactinaemia is about 30%. The mean plasma follicle-stimulating hormone was abnormally low both in patients with anorexia nervosa and simple weight loss, while the mean plasma luteinizing hormone was depressed only in patients with anorexia nervosa. This difference is compatible with a more profound hypothalamic disorder in anorexia nervosa, which is not solely dependent on the weight loss, than in amenorrhoea due to simple dieting.