The human body is not a set of organs and systems. This is a complex biological system connected by regulatory mechanisms of the nervous and endocrine nature. And one of the main structures in the system of regulation of the body's activity is the hypothalamic-pituitary system. In the article we will consider the anatomy and physiology of this complex system. Let's give a brief description of the hormones that are secreted by the thalamus and hypothalamus, as well as a brief overview of the disorders of the hypothalamic-pituitary system and the diseases they lead to.
Thalamus - pituitary gland: connected by one chain
Combining the structural components of the hypothalamus and pituitary gland into a single system ensures the regulation of the basic functions of our body. In this system, there are both direct and reverse connections, whichregulate the synthesis and secretion of hormones.
The hypothalamus directs the work of the pituitary gland, and feedback is carried out through the hormones of the endocrine glands, which are released under the action of pituitary hormones. Thus, the peripheral endocrine glands with the blood flow bring their biologically active substances to the hypothalamus and regulate the secretory activity of the hypothalamic-pituitary system of the brain.
Recall that hormones are protein or steroid biological substances that are secreted into the blood by endocrine organs and regulate metabolism, water and mineral balance, growth and development of the body, and also take an active part in the body's response to stress.
A bit of anatomy
The physiology of the hypothalamic-pituitary system is directly related to the anatomical structure of the structures that it includes.
The hypothalamus is a small part of the intermediate part of the brain, which is formed by more than 30 clusters of nerve cells (nodes). It is connected by nerve endings to all parts of the nervous system: the cerebral cortex, hippocampus, amygdala, cerebellum, brain stem and spinal cord. The hypothalamus regulates the hormonal secretion of the pituitary gland and is the link between the nervous system and the endocrine system. The feeling of hunger, thirst, thermoregulation, sexual desire, sleep and wakefulness - this is not a complete list of the functions of this organ, the anatomical boundaries of which are not clear, and the mass is up to 5 grams.
The pituitary gland is a rounded formation on the lower surface of the brain, weighing up to 0.5 grams. This is the central organ of the endocrine system, its "conductor" - it turns on and off the work of all the secretion organs of our body. The pituitary gland consists of two lobes:
- Adenohypophysis (anterior lobe), which is formed by glandular cells of various types that synthesize tropic hormones (aimed at a specific target organ).
- The neurohypophysis (posterior lobe), which is formed by the endings of the neurosecretory cells of the hypothalamus.
Due to this anatomical structure, the hypothalamic-pituitary system is divided into 2 sections - the hypothalamic-adenohypophyseal and the hypothalamic-neurohypophyseal.
The most important
If the pituitary gland is the "conductor" of the orchestra, then the hypothalamus is the "composer". Two main hormones are synthesized in its nuclei - vasopressin (diuretic) and oxytocin, which are transported to the neurohypophysis.
In addition, releasing hormones are secreted here, which regulate the formation of hormones in the adenohypophysis. These are peptides that come in 2 types:
- Liberins are releasing hormones that stimulate the secretory cells of the pituitary gland (somatoliberin, corticoliberin, thyreoliberin, gonadotropin).
- Statins are hormone-inhibitors that inhibit the work of the pituitary gland (somatostatin, prolactinostatin).
Releasing hormones not only regulate the secretory function of the pituitary gland, but also affect the functioning of nerve cells in different parts of the brain. Many of them have already been synthesized andhave found their application in therapeutic practice in the correction of pathologies of the hypothalamic-pituitary system.
The hypothalamus also synthesizes morphine-like peptides - enkephalins and endorphins, which reduce stress and provide pain relief.
The hypothalamus receives signals from other brain structures using amino-specific systems and thus provides a link between the nervous and endocrine systems of the body. Its neurosecretory cells act on the cells of the pituitary not only by sending a nerve impulse, but also by releasing neurohormones. This receives signals from the retina, olfactory bulb, taste and pain receptors. The hypothalamus analyzes blood pressure, blood glucose levels, the state of the gastrointestinal tract and other information from the internal organs.
Working principles
The regulation of the hypothalamic-pituitary system is carried out according to the principles of direct (positive) and feedback (negative) connection. It is this interaction that ensures self-regulation and normalization of the body's hormonal balance.
Neurohormones of the hypothalamus act on the cells of the pituitary gland and increase (liberins) or inhibit (statins) its secretory function. This is a direct link.
When the level of pituitary hormones in the blood rises, they enter the hypothalamus and reduce its secretory function. This is feedback.
This is how the neurohormonal regulation of body functions is ensured, the constancy of the internal environment is ensured, the coordination of vital processes andadaptability to environmental conditions.
Hypothalamo-adenohypophyseal region
This department secretes 6 hormones of the hypothalamic-pituitary system, namely:
- Prolactin or luteotropic hormone - stimulate lactation, growth and metabolic processes, the instincts of caring for offspring.
- Thyrotropin - provides regulation of the thyroid gland.
- Adenocorticotropin - regulates the production of glucocorticoid hormones by the adrenal cortex.
- 2 gonadotropic hormones - luteinizing (in men) and follicle-stimulating (in women), which are responsible for sexual behavior and functions.
- Somatotropic hormone - stimulates protein synthesis in cells, affects the overall growth of the body.
Hypothalamo-Neuropituitary Department
This department performs 2 functions of the hypothalamic-pituitary system. The posterior pituitary secretes the hormones asparotocin, vasotocin, valitocin, glumitocin, isotocin, and mezotocin. They play an important role in metabolic processes in the human body.
In addition, in this department, vasopressin and oxytocin received from the hypothalamus are deposited in the blood.
Vasopressin regulates the processes of water excretion by the kidneys, increases the tone of the smooth muscles of internal organs and blood vessels, and is involved in the regulation of aggression and memory.
Oxytocin is a hormone of the hypothalamic-pituitary system, whose role is to stimulate uterine contractions during pregnancy, stimulate sexual desire and trust between partners. Thisthe hormone is often referred to as the “hormone of happiness.”
Diseases of the hypothalamic-pituitary system
As it has already become clear, the pathology of this system is associated with disturbances in the normal activity of one of its departments - the hypothalamus, the anterior and posterior parts of the pituitary gland.
Any change in the hormonal balance in the body leads to serious consequences in the body. Especially when the "composer" or "conductor" makes mistakes.
In addition to hormonal disruptions, the causes of pathologies in the hypothalamus-pituitary gland system can be oncological neoplasms and injuries that affect these areas. It is impossible to enumerate all the diseases one way or another connected with this regulatory system. We will focus on the most significant pathologies and give a brief description of them.
Dwarfism and Gigantism
These growth disorders are associated with disorders in the production of growth hormone.
Pituitary dwarfism is a disease associated with somatotropin deficiency. It manifests itself in a lag in growth and development (physical and sexual). The etiology of the disease is associated with hereditary factors, birth defects, trauma and pituitary tumors. However, in 60% of cases, the causes of dwarfism cannot be established. The therapy is associated with the constant intake of growth hormones by patients.
Pituitary gigantism is a disease associated with an excess or increased activity of growth hormone. It develops more often after 10 years, and the predisposing factors are neuroinfections, inflammation indiencephalon, trauma. The disease manifests itself in accelerated growth, features of acromegaly (enlargement of the limbs and facial bones). Estrogens and androgens are used for therapy.
Adiposogenital dystrophy
The causes of this pathology can be intrauterine infections, birth injuries, viral infections (scarlet fever, typhoid), chronic infections (syphilis and tuberculosis), tumors, thrombosis, cerebral hemorrhages.
The clinical picture includes underdevelopment of the genital organs, gynecomastia (enlargement of the mammary glands due to the deposition of fat) and obesity. More common in boys aged 10-13.
Itsenko-Cushing's disease
This pathology develops when the hypothalamus, thalamus and reticular formation of the brain are affected. The etiology is associated with injuries, neuroinfections (meningitis, encephalitis), intoxications and tumors.
The disease develops due to excessive secretion of corticotropin by the adrenal cortex.
With this pathology, patients report weakness, headaches, pain in the limbs, drowsiness and thirst. Pathology is accompanied by obesity and short stature, puffiness of the face, dry skin with characteristic stretch marks (stretch marks).
Erythrocytes are increased in the blood, blood pressure is increased, tachycardia and dystrophy of the heart muscles.
Treatment is symptomatic.
