Physiologic and pathologic production of milk involves complex relations between the mammary glands, hormones, and the central nervous system. In all the galactorrhea syndromes there is a functional or mechanical problem at the pituitary level, with abnormal secretion or reserve of prolactin secretion. Stimulatory agents of prolactin, like thyrotropin releasing hormone (TRH), chlorpromazine, amino acids, and insulin, can be helpful in the study of the hypothalamic pituitary functional reserve, while the osmotic tests seem to provide a clear distinction between functional and tumoral causes. The inhibitoryagents of prolactin secretion, L-dopa and CB 154, permit the study of the negative control of the hormone. In addition, CB 154 appears to be an effective treatment for functional galactorrhea. hyperprolactinemia appears to exert an inhibitory influence on gonadotropins. Clomiphene, acting on the hypothalamus, and LHIRH, acting on the gonadotropes, permit the assessment of the gonadotropic hypothalamic-hypophyseal axis.