THEME: THE THYMUS GLAND AS AN ORGAN OF THE ENDOCRINE SYSTEM. PHYSIOLOGY OF THE THYMUS

Views on the hormonal role of the thymus gland in the body have undergone significant changes depending on the level of our knowledge about its structure and functions. At first, it was attributed entirely to the endocrine system, then to the lymphoid system. With the development of immunology and the emergence of evidence of the primary regulatory function of the thymus in immune reactivity, the question of the hormonal mechanism of action arose again. This view was supported by the fact that neonatal thymectomy causes not only changes in immune activity, but also the development of the so-called Wasting syndrome (exhaustion syndrome), which is essentially a reflection of slowed metabolic processes and a lag in the animal's physical development and growth. The conclusion about the influence of the thymus on the growth processes was made on the basis of the fact that in newborns and young animals it is larger than in adults. This is due to the involution (reverse development) of the thymus gland, which is accompanied by a decrease in the number of thymic epithelial cells and, as a consequence, a decrease in endocrine properties. In addition, two substances isolated from the tissue of the gland have been described with an effect that stimulates and inhibits growth processes (but this is a controversial issue). In any case, the thymus gland cannot affect growth without the presence of growth hormone, on the other hand, with thymectomy, the effect of growth hormone on growth is significantly reduce