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The role of hormones in the development of cancer
Last reviewed: 19.11.2021
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Hormones, like carcinogens, affect the cell both through the body (indirectly) and directly, exerting a direct effect on its genetic apparatus. Hormones contribute to the reduction of antitumor immunity, resulting in favorable conditions for the development of malignant neoplasms.
How do hormones cause cancer?
The disturbance of hormonal homeostasis, caused by changes in the functioning of the neuroendocrine system, contributes to the development of cancer. This mechanism is widely covered in the literature with reference to violations arising from the primary deficiency of certain hormones. For example, hypothyroidism can cause a diffuse or nodular goiter, and unilateral oophorectomy is the cause of cystic changes in the remaining ovary. In these cases, the mechanism that promotes the development of the pathological process can be designated as a peripheral type of homeostatic failure. Accordingly, the measure of prevention and treatment in such situations is substitution therapy with appropriate hormones.
At the same time, in the process of normal aging and under the influence of a number of factors that intensify the aging process, the mechanism of hormonal disorders that promote carcinogenesis has a different character. In these cases, the violation of hormonal equilibrium primarily arises not because of a lack of peripheral hormone, but is a consequence of a decrease in the sensitivity of the central (hypothalamic-pituitary) link of the homeostatic system to the action of the corresponding peripheral hormone by the mechanism of negative feedback. Accordingly, this type of disturbance of homeostasis was designated as the central type of homeostatic failure. Such relationships are clearly visible in the reproductive system, which is manifested by an increase in blood levels of gonadotropins, especially follicle-stimulating hormone (FSH). This shift reproduces, due to proliferative effects on ovarian tissue, one of the conditions conducive to the development of tumors. This can explain why the use of steroid contraceptives, which not only prevent ovulation, but also reduce the concentration of gonadotropins in the blood, reduces the incidence of ovarian tumors.
Hormonal status is a factor determining the risk of many malignant tumors, especially the breast, the uterus, the ovaries, the prostate and the testicle. In the structure of morbidity malignant neoplasms in Russia, hormone-dependent tumors account for 17.6%. A hormone-dependent malignant tumor develops as a result of excessive (excessive) hormonal stimulation of the organ, normal growth, the development and function of which is controlled by a steroid or polypeptide hormone. The division of tumors into hormone-dependent and hormone-independent is conditional, since the division of cells of any tissue is controlled by hormonal factors.
Experimental studies and clinical observations indicate a carcinogenic effect of estrogens on the body. The involvement of estrogens in the process of hormonal carcinogenesis is reduced to the fulfillment of the role of promotional factors (primarily as inducers of increased proliferation and inhibitors of apoptosis) and initiation, which are most often mediated (in particular, through the formation of free radical metabolic products of classical estrogens, so-called catechol estrogens) DNA.
In women, the total level of estrogenic stimulation throughout life depends on the age of menarche and menopause and on the number of ovulations. The latter in turn is determined by the number of pregnancies. Pregnancy, as, indeed, oral contraceptives containing progesterone, lead to suppression of ovulation and, accordingly, a decrease in the estrogen stimulation of hormone-dependent organs, reducing the risk of developing malignant neoplasm.
The hormonal status of women is also influenced by the age of the first birth, the number of births, the use of oral contraceptives and other hormonal drugs.
Androgens contribute to the development of prostate cancer. Hypothyroidism is the background that facilitates the onset of cancer.
Corticosteroid hormones have a common catabolic effect, contribute to a decrease in the synthesis of proteins and increase their transition to carbohydrates, lowering tissue resistance and enhancing metastasis.
Growth hormone also has a big impact on tumor growth. This is due to the fact that growth hormone enhances the differentiation and growth of cells, accelerates their proliferation, increases the number of mitoses. As a result, under its influence, growth and metastasis of all types of experimental tumors in animals is stimulated.