ENDOCRINE CONTROL OF THE MAMMARY GLAND

Abstract

During the past few years no phase of experimental endocrinology has been more rapidly developed than that which deals with the harmonic factors involved in the development and function of the mammary glands. The quarter century preceding 1928 saw very little advance in the understanding of lactation phenomena over the purely casuistic analyses of Halban (1905) and the experimental studies of Ancel and Bouin (1911). Since the introduction of a new factor, the anterior pituitary, and the advent of purified ovarian hormone preparations in general use, the experimental laboratories have yielded a steady flow of new facts relating to the endocrine physiology of the mammary glands. A great deal of important progress has been made and we are now in a position to understand many of the factors concerned in the control of lactation, yet many puzzling questions remain. Even now, some of them are being explained; no doubt others will soon be solved. Mean-while, it may be profitable to examine the position of the general prob-lem. If it is complex, it is only because the problem which originally appeared very simple has been shown, during its evolution under experi-mental attack, to possess aspects of a totally unforeseen nature, As indicated in the title, this review limits itself to the harmonic fac-tors concerned in lactation. It would be valuable to consider some of the more purely metabolic and general physiological processes con-tributing to the secretion of milk, but this falls outside the scope of the present article. The changes which occur in the female mammary gland may be con-veniently divided into six phases, viz., prenatal, birth to puberty, recur-ring sexual cycles, pregnancy, lactation, and involution. In this review we will consider those changes which normally occur during the sexual cycles, pregnancy, and lactation, and in their experimental reproduction. In order to furnish a basis for discussion, it may be of interest to review briefly the glandular characteristics of the mammae. The fully de-veloped mammary gland is a compound tubulo-alveolar gland. A vari-able number of lactiferous or lobar ducts radiate from the nipple and