The role of hormones in cancer development

Hormones, like carcinogens, affect the cell both through the body (indirectly) and directly, exerting a direct effect on its genetic apparatus. Hormones help reduce antitumor immunity, which creates favorable conditions for the development of malignant neoplasms.

How do hormones cause cancer?

Hormonal homeostasis disturbance caused by changes in the functioning of the neuroendocrine system contributes to the development of cancer. This mechanism is widely described in the literature in relation to disturbances arising from primary deficiency of certain hormones. For example, hypothyroidism can cause the development of diffuse or nodular goiter, and unilateral ovariectomy can cause cystic changes in the remaining ovary. In these cases, the mechanism contributing to the development of the pathological process can be designated as a peripheral type of homeostatic insufficiency. Accordingly, the preventive and therapeutic measure in such situations is replacement therapy with the corresponding hormones.

At the same time, in the process of normal aging and under the influence of a number of factors intensifying the aging process, the mechanism of hormonal disturbances that promote carcinogenesis has a different character. In these cases, the disturbance of hormonal balance primarily occurs not due to a deficiency of a 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 homeostasis disturbance was designated as the central type of homeostatic insufficiency. Similar relationships are clearly detected in the reproductive system, which is manifested by an increase in the blood level of gonadotropins, especially follicle-stimulating hormone (FSH). This shift reproduces, due to the proliferative effect on ovarian tissue, one of the conditions that promote the development of tumors. This may 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, primarily of the mammary gland, uterine body, ovaries, prostate gland and testicle. In the structure of malignant neoplasm incidence in Russia, hormone-dependent tumors account for 17.6%. A hormone-dependent malignant tumor develops as a result of increased (excessive) hormonal stimulation of an organ, the normal growth, development and function of which is under the control of a particular steroid or polypeptide hormone. The division of tumors into hormone-dependent and hormone-independent is conditional, since cell division of any tissue is controlled by hormonal factors.

Experimental studies and clinical observations indicate the carcinogenic effect of estrogens on the body. The participation of estrogens in the process of hormonal carcinogenesis is reduced to their role as promotion factors (primarily as inducers of increased proliferation and inhibitors of apoptosis) and initiation, capable most often of indirectly (in particular, through the formation of free radical products of the metabolism of derivatives of classical estrogens - the so-called catecholestrogens) damaging DNA.

In women, the total level of estrogenic stimulation during life depends on the age of menarche and menopause and the number of ovulations. The latter in turn is determined by the number of pregnancies. Pregnancy, as well as oral contraceptives containing progesterone, lead to suppression of ovulation and, accordingly, a decrease in estrogenic stimulation of hormone-dependent organs, reducing the risk of developing a malignant neoplasm.

A woman's hormonal status is also influenced by the age at first birth, the number of births, the use of oral contraceptives and other hormonal drugs.

Androgens promote the development of prostate cancer. Hypothyroidism is a background that facilitates the occurrence of cancer.

Corticosteroid hormones have a general catabolic effect, contribute to a decrease in protein synthesis and an increase in their conversion into carbohydrates, reducing tissue resistance and increasing metastasis.

Growth hormone also has a great influence on tumor growth. This is due to the fact that growth hormone enhances differentiation and growth of cells, accelerates their proliferation, and increases the number of mitoses. As a result, under its influence, growth and metastasis of all types of experimental tumors in animals are stimulated.