This article presents an overview of prolactin (PRL) participation in the development of mammary gland pathology. Significance of the problem is determined by the general increase in the number of breast cancer. Violation of hormonal regulation is an important factor in the development of breast cancer and tumors of other localizations in the human reproductive system. A significant role in this imbalance is played by PRL. The purpose of the study was to conduct a literature review to determine the role of prolactin in the development of breast cancer. Prolactin is a polypeptide hormone that is synthesized and excreted from the lactotrophic cells of the anterior part of the pituitary gland. Outside the pituitary gland, PRL is encoded by the endometrium, decidual envelope, the lymphocytes, by the central nervous system, mammary gland and the prostate, where it acts as a cytokine. Secretion of PRL is regulated by dopaminergic, adrenergic, cholinergic, and also serotonergic units of the autonomic nervous system. In the mammary gland, PRL exists as a circulating pituitary hormone and in the form of a hormone produced by the epithelium duct. In breast prolactin binds to the cell’s surface of the prolactin receptor (PRL-R). There are six isoforms of PRL-R that determine the effects of prolactin in human tissue. The main effects of PRL in the tissue of mammary gland are mammogenesis, lactogenesis and galactopoietics. Increased level of PRL in biological fluids and body tissues plays an important role in breast pathology. High levels of prolactin hormone are more inherent to young women than menopausal women, because of reducing estrogen exposure and inhibiting lactothorophytic cells. In general, hyperprolactinemia can affect not only the pathology of mammary gland, but also cause abnormalities in the reproductive system, causing anovulatory cycles, amenorrhea, and infertility. Pathological manifestations in breast tissues can be caused not only by the blood prolactin circulating, but also the PRL, which is secreted by own mammary gland tissues, which is one of the factors of carcinogenesis and has great importance in the breast cancer development. PRL increases proliferative activity of the mammary gland cells and affects the regulation of apoptosis. It acts as a pro-oncogen in early neoplastic transformation, progression and forms a resistance to cancer treatment. Besides increased expression of prolactin receptor, it also leads to increased proliferation and invasive tumor growth, and conversely the PRL-R antagonist leads to a decrease clonogenic activity of the cells of breast cancer and potentiated the effect of cytotoxic drugs. Consequently, expression of prolactin receptor may be a marker for the differentiation of epithelial cells of the affected mammary gland. Conclusions. Further investigation of the pathogenetic mechanisms and their effect of PRL expression on the tissue of mammary gland can greatly contribute for the development of new methods of diagnosing and treating breast cancer.
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