HORMONES AND OTHER FACTORS CONTROLLING GROWTH IN THE MAMMARY GLAND: A REVIEW.

Among the many factors that control mammary gland growth, hormones play a leading role. To assess the importance of each factor on the growth of the gland, different methods have been devised. These methods are complementary hence no method is capable by itself of a total estimate of mammary growth. Fetal growth of the mammary rudiment is influenced by hormonal factors and at the same time (more than at any other stage of mammary growth) by the mesenchyme. A marked characteristic of the fetal period is the establishment of sexual dimorphism. This peculiar phenomenon has been studied in vitro. After birth, the gland falls under the direct control of stimuli from the hypothalamus pituitary axis. By means of its cyclic variations or changes conditioned by conception, growth is induced by pituitary hormones proper (prolactin growth hormone) or via the ovary or the adrenals. Other factors such as diet, age, mesenchyme, and genetic background modulate the action of hormones on the gland. The action of all these factors is examined in this paper throughout the life of different mammals, from the prepuberal stage, through adult nulliparous life, gestation, the maximal growth induced by the hormonal levels of lactation, and in regression (produced alter hormone removal). In vivo and in vitro studies have been correlated in demonstrate which of the stimuli induce mammary cell replication and growth in the preneoplastic and neoplastic mammary gland. [ABSTRACT FROM AUTHOR]