The endocrine system in children

The endocrine system in children has a very complex multi-level structure and multi-circuit regulation with the capabilities of both external control through mechanisms of adaptation to environmental factors and internal homeostasis through negative feedback chains. The latter are often based on the regulation of the formation or release of a hormone due to a decrease in its content in the blood or, conversely, an increase in hormone production with its increased consumption and a decrease in concentrations. However, there are also mechanisms that change the thresholds of this reaction by changing the sensitivity of receptors to circulating hormones. A classic example is the triggering of puberty events with a decrease in the sensitivity of receptors to sex steroids.

Molecules that change the level of functional activity or the direction of activity of some groups of cells or tissues are very widely represented in physiology. Some of these molecules are produced by the regulated cells or tissues themselves (autocrine regulation), some of them are produced in closely located and often related in structure and function cells and tissues (paracrine regulation). At the same time, highly specialized regulatory organs have emerged in evolution, forming signal molecules that spread humorally and affect the entire set of some specialized cells or tissues, regardless of their close or distant localization to the hormone-producing cells. This is commonly called endocrine regulation, and the cells that form such molecules and the organs that unite such cells are referred to as endocrine glands.

Endocrine mechanisms of regulation of physiological functions can be divided into several levels. The highest is the neurogenic or hypothalamic level and, perhaps, levels of an even higher order, such as the thalamic level, the level of the reticular formation or rhinencephalic formations as a whole, the limbic-reticular complex and the new cortex, which provide integrative functions of the brain. The stimulus for these levels and formations are information signals or effects emanating from the external or internal environment of the organism. The response of this level of regulation is the inclusion or non-inclusion of certain vegetative structures and apparatuses, as well as groups or individual endocrine glands. All this together is usually attributed to suprasegmental levels of regulation, in which there is no division into sympathetic and parasympathetic, vegetative and endocrine components. The division of suprasegmental systems, structures and levels of regulation into "ergotropic" and "trophotropic" is recognized. Each of these levels or settings of regulation fundamentally and comprehensively, i.e. precisely integratively, changes the entire orientation and structure of life processes. It is here, at the level of rhinencephalic structures, that “decision making” and “setting of a way of life” that is optimal for the child at the present time occur. Following the terminology of A. M. Vein, there is a choice between “ergotropic” and “trophotropic” forms of behavior. By greatly simplifying the meaning of the most complex biological regulations, we can speak of two “ways of life” that constitute an alternative.

Ergotropic and trophotropic forms of behavior (according to A. M. Vein, with changes)

Indicators	Ergotropic behavior	Trophotropic behavior
Behavior itself	Adaptation to a changing environment, fear of separation, uncertainty and expectation, sleep disturbances, readiness and mobilization to flee or attack	Peace and comfort, relaxation, acceptance of the environment. Realization of growth and development processes, cognitive activity, learning ability, memory, sleep support
Leading vegetative system	Sympathetic	Parasympathetic
Reactions of the limbic-reticular complex	Mental activation. Endocrine activation: somatostatin, ACTH, antidiuretic hormone, cortisol, catecholamines. EEG desynchronization, increased muscle tone	Mental relaxation. Endocrine activation: STH, IGF-R, oxytocin, growth peptides, gastrin, cholecystokinin

In the case of a relatively favorable environmental environment and psycho-emotional state, in the absence of external and internal stress factors, the central regulatory mechanisms are set to "trophotropic" activity - to anabolism, intensive growth and tissue differentiation, to activate memory and learning mechanisms, to curiosity and exploratory behavior. This complex is launched through the inclusion of neuroendocrine chains associated with growth hormone, other growth factors, relaxation peptides and cholecystokinin. This is the dominant set of properties of normal life and normal development of a child of any age with the leading role of parasympathetic activation.

The switchover of the installation must be carried out in the shortest possible time when the situation changes, when a stress stimulus, acute discomfort or threat is perceived. This will already be the inclusion of complex emergency survival systems with the dominance of the components of the "ergotropic" system with the leading participation of sympathetic activation, ACTH, catecholamines and corticosteroids. The tasks of development here recede into the background or are removed altogether, catabolism dominates over anabolic processes. Insufficiency of switching reactions, delay in switching in the case of a real threat to the child's life can create or multiply the risk of loss of life, even for children who are practically healthy and prosperous in all respects. Experienced pediatricians know that with some acute infections the risk of a fatal outcome, mainly sudden death, is especially high in previously the healthiest, well-developed young children. An infection that suddenly catches such a child may not encounter a powerful glucocorticoid defense system and is quickly realized by hemodynamic disorders, shock and edema-swelling of the brain. This inability to quickly turn on protective stress mechanisms in children during infections and its connection with the phenomenon of "mors thymica" was described by the outstanding Russian pediatric pathologist T. E. Ivanovskaya. All of the above is directly related to both the medical tactics of intensive treatment of children with a catastrophic course of acute infections and the practice of forming children's health. In pediatric practice, there is another form of inadequate manifestation of the ergotropic reaction in acute infections - this is hypersecretion of antidiuretic hormone, or syndrome of inadequate release of vasopressin. In this case, manifestations of Parkhon's disease are noted - cessation of urination, increasing edematous syndrome in the complete absence of thirst. Edema can also spread to the respiratory tract affected by viral inflammation. This results in a peculiar broncho-obstructive syndrome.

It is obvious that in the system of raising a healthy child there should be a place for some training method for the rhinencephalic switch of the way of Life. Both anti-stress and pro-stress education and training are necessary.

Most of the humoral factors produced at the hypothalamus level are called "liberating" or "releasing" factors, and are referred to as "liberins". The following hypothalamic hormones have been studied the most:

• somatostatin;
• somatoliberin;
• corticoliberin;
• prolactostatin;
• gonadotropin-releasing hormone;
• thyroliberin.

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