Prolactin and mammary gland carcinogenesis. The problem of human prolactin

Abstract The ultimate objective of experimental cancer research must be to apply the findings obtained to the prevention or treatment of the disease in humans. In this review it is shown that prolactin is suspected of being one of the hormones mainly responsible for the development of mammary carcinoma in mice. Investigations into the question of whether this might also be true in man are hampered by the fact that the existence of prolactin in this species is still a matter of debate. Because of the intrinsic prolactin‐like activity of purified human growth hormone, the need for the presence of prolactin as a separate hormone might be questioned. It is shown, however, on the basis of a number of biological arguments and clinical observations, that it is extremely unlikely that all prolactin‐like effects in man are due to one of the manifold activities of growth hormone alone; consequently the urgent need to analyse the role of prolactin as a separate hormone in man becomes evident, especially in the field of breast cancer. Tentatively, ways are indicated by which this objective might be reached.