About 30% of amenorrhoeic women have a disturbed prolactin secretion. In about 10% the cause is a hypophyseal-suprahypophyseal tumour. Taking into consideration the degree of severity of the galactorrhoe, the amenorrhoe is connected with incontinence of milk. Also disturbances of the male potency may with partly similar symptomatology be conditioned by a hyperprolactaemia. For the development of hypogonadism the physiologic effect of prolactin gives sufficient explanations. With the introduction of dopaminergic substances which influence the disturbed regulating circle hypothalamus-hypophysis in the sense of an inhibition of the prolactin secretion new conservative possibilities for the therapy of disturbances of fertility are the result. With adequate recommendations for the radioimmunologic determination of prolactin the WHO made allowance for the central position of prolactin in the pathogenesis of hypogonadism. In particular the existence of hypophyseal microadenomas presumes a close cooperation between gynaecologists, radiologists, ophthalmologists and endocrinologists in the clarification of hyperprolactinaemic disturbances of fertility.