The pituitary prolactinoma syndrome and the mythology of hyperprolactinaemia.

The use of the term 'hyperprolactinaemia' is critically examined. In addition to technical and statistical factors that affect the interpretation of prolactin levels, the concept of the 'normal range' is shown to be misleading. An alternative approach is proposed in which the clinical significance of different prolactin levels is carefully defined in different clinical situations thereby giving the clinician an indication of their predictive value. Only in this way can the individual patient be given appropriate advice and, if necessary, therapy.