Mammary Growth Regulation by Transforming Growth Factor β

Abstract

A considerable literature has developed around the problem of regulation of mammary development. The great majority of this work has concerned the identification of systemic mammogens, notably the ovarian steroids, pituitary peptides, adrenal corticoids, and placental factors (1). The distinguishing feature of these hormones is that they all drive mammary development towards growth or functional differentiation; that is, they act as positive regulators. The existence of these hormones has been, by and large, demonstrated in vivo by endocrine ablation surgery followed by replacement therapy, in which removal of endocrine secretion interrupted the normal development or function of the organ. Because these experiments were conducted in a physiological setting, their biological significance was never in doubt. The present situation is that the naturally occurring mammogens have been identified and described in considerable detail and, when more recent biochemical and molecular approaches are factored in, it can be said that we are developing a usable outline of the hormones driving mammary growth and function.