The human body is not a set of organs and systems. This is a complex biological system, connected by regulatory mechanisms of a 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 consider the anatomy and physiology of this complex system. We 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: Single Chain
The combination of 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 feedbacks that regulate the synthesis and secretion of hormones.
The hypothalamus directs the pituitary gland, and feedback is provided through the hormones of the endocrine glands, which are secreted by the action of the pituitary hormones. Thus, peripheral endocrine glands with blood flow bring their biologically active substances into 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 the organs of internal secretion (endocrine) 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 enter it.
The hypothalamus is a small part of the intermediate part of the brain, which is formed by more than 30 accumulations of nerve cells (nodes). It is connected by nerve endings to all parts of the nervous system: cerebral cortex, hippocampus, tonsil, cerebellum, brain stem and spinal cord. The hypothalamus regulates the hormonal secretion of the pituitary gland and is the connecting link between the nervous system and the endocrine. Feeling of hunger, thirst, thermoregulation, sex drive, sleep and wakefulness - this is not a complete list of the functions of this body, the anatomical boundaries of which are not clear, but weigh up to 5 grams.
The pituitary gland is a round 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 organs of secretion 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).
- Neurohypophysis (posterior lobe), which is formed by the ends of the neurosecretory cells of the hypothalamus.
In connection with this anatomical structure in the hypothalamic-pituitary system, 2 departments are distinguished - the hypothalamic-adenohypophysial and hypothalamic-neurohypophysial.
The main
If the pituitary gland is the "conductor" of the orchestra, then the hypothalamus is the "composer". In its nuclei, two main hormones are synthesized - vasopressin (diuretic) and oxytocin, which are transported to the neurohypophysis.
In addition, releasing hormones that regulate the formation of hormones in the adenohypophysis are secreted here. These are peptides, which are of 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 pituitary gland (somatostatin, prolactin statin).
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 and have found their application in therapeutic practice in the correction of pathologies of the hypothalamic-pituitary system.
Morphine-like peptides are synthesized in the hypothalamus - enkephalins and endorphins, which reduce stress and anesthetize.
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 pituitary cells not only sending a nerve impulse, but also secreting neurohormones. It receives signals from the retina, olfactory bulb, taste and pain receptors. The hypothalamus analyzes blood pressure, blood glucose, the state of the gastrointestinal tract and other information from internal organs.
Work principles
The regulation of the hypothalamic-pituitary system is carried out according to the principles of direct (positive) and feedback (negative) communication. It is this interaction that ensures self-regulation and normalization of the hormonal balance of the body.
The hypothalamic neurohormones act on the pituitary cells 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 decrease its secretory function. This is feedback.
This is how the neuro-hormonal regulation of body functions is ensured, the constancy of the internal environment, coordination of vital processes and adaptability to environmental conditions are ensured.
Hypothalamic-adenohypophysial division
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 function.
- Growth hormone - stimulates the synthesis of protein in cells, affects the overall growth of the body.
Hypothalamic-neurohypophysial division
This department performs 2 functions of the hypothalamic-pituitary system. The hormones asparotocin, vasotocin, valitocin, glumitocin, isotocin, mesotocin are secreted in the back of the pituitary gland. They play an important role in metabolic processes in the human body.
In addition, in this section, vasopressin and oxytocin received from the hypothalamus are deposited in the blood.
Vasopressin regulates the processes of water excretion by the kidneys, increases the smooth muscle tone of the 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. This hormone is often called the "hormone of happiness."
Diseases of the hypothalamic-pituitary system
As it has already become clear, the pathology of this system is associated with violations of the normal activity of one of its departments - the hypothalamus, anterior and posterior pituitary gland.
Any change in the hormonal balance in the body leads to serious consequences in the body. Especially when mistakes are made by the “composer” or “conductor”.
In addition to hormonal disruptions, oncological neoplasms and injuries that affect these areas can be the causes of pathologies in the hypothalamus-pituitary system. All diseases, one way or another connected with this regulatory system, are impossible to list. 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 that is associated with growth hormone 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, injuries and tumors of the pituitary gland. However, in 60% of cases, the causes of dwarfism cannot be established. 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 predisposing factors are neuroinfection, inflammation in the diencephalon, and trauma. The disease manifests itself in accelerated growth, features of acromegaly (an increase in limbs and facial bones). For therapy, estrogens and androgens are used.
Adiposogenital dystrophy
The causes of this pathology can be intrauterine infections, birth injuries, viral infections (scarlet fever, typhoid), chronic infections (syphilis and tuberculosis), tumors, thromboses, cerebral hemorrhages.
The clinical picture includes underdevelopment of the genitals, gynecomastia (an increase in the mammary glands due to the deposition of fat) and obesity. It is more common in boys 10-13 years old.
Itsenko-Cushing's Disease
This pathology develops with damage to the hypothalamus, thalamus, and the reticular formation of the brain. The etiology is associated with injuries, neuroinfections (meningitis, encephalitis), intoxications and tumors.
The disease develops in connection with excessive secretion of corticotropin by the adrenal cortex.
With this pathology, patients report weakness, headaches, limb pain, drowsiness, and thirst. Pathology is accompanied by obesity and stunting, puffiness of the face, dry skin with characteristic stretch marks (striae).
Red blood cells are increased, blood pressure is increased, tachycardia and dystrophy of the heart muscles.
The treatment is symptomatic.