The pituitary gland is an endocrine gland whose proper function is essential for the proper functioning of the body. Hormones secreted by this organ control, among others the course of growth processes, but also they are associated with phenomena related to reproduction or affect the activity of the thyroid gland and adrenal glands.

The pituitary gland(Latinhypophysis , Eng.pituitary gland ) is one of the the most important glands of the endocrine system. This organ usually does not exceed one gram of weight, and at the same time it controls the activity of vital organs, such as the thyroid gland or adrenal glands. The proper function of the pituitary gland is essential for the proper functioning of the body - diseases can be caused by both hypopituitarism and conditions in which there is an increased release of pituitary hormones - hyperfunction of the pituitary gland. organs included in its composition. Various phenomena influence the secretion of various substances, but the primary centers controlling the release of various hormones are the hypothalamus and the pituitary gland.

Przysadka: location and construction

The human pituitary gland is about the size of a pea or a cherry, usually the weight of this gland is around 0.5 grams. The organ is located in the central fossa of the skull, it is considered part of the diencephalon and it is located in the cavity of the sphenoid bones, which is known as the Turkish saddle. Bone structures surround the pituitary gland on all sides except the upper one - from the top, the gland covers the dura mater extension, known as the diaphragm of the Turkish saddle. The pituitary gland is generally divided into three lobes: anterior, intermediate and posterior. Some authors who analyze the structure of the pituitary gland ignore the existence of the middle lobe because it is actually residual in humans. The anterior and posterior lobe is distinguished not only by the hormones they secrete, but also by the origin of these parts of the pituitary gland. The anterior lobe of the pituitary gland develops from the epithelium of the secondary palate and accounts for about 80% of the mass of the entire organ. The posterior lobe of the gland, in turn, develops from the structures of the hypothalamus and it really belongs to this organ - the posterior pituitary lobe has a direct connection with the hypothalamus, boththe endocrine glands are connected with each other through the so-called funnel.

Pituitary: Anterior pituitary gland hormones

The anterior pituitary gland is also referred to as the glandular gland. This part of the pituitary gland plays an extremely important role, as it secretes the so-called tropic hormones that control the function of other endocrine glands: the thyroid gland, adrenal glands or (respectively for the given sex) ovaries and testes.

There are 5 different types of cells in the pituitary gland - each type of cell in this gland produces a different hormone. In this division, the following cells are distinguished:

  • somatotropic: they are the most numerous population of cells in the anterior pituitary gland (up to 40% of all cells in this part of the gland), they secrete growth hormone (GH)
  • corticotropic: their share in the total mass of the glandular gland is about 20%, they produce corticotropin (ACTH), influencing the function of the adrenal glands

In the case of the remaining populations of the anterior pituitary gland cells, each of them accounts for up to 5% of the total mass of this part of the gland, and they are cells:

  • thyrotropin: they produce thyroid stimulating hormone (TSH), which controls thyroid function,
  • gonadotrophic: they secrete lutropin (LH) and follicle stimulating hormone (FSH) which influence the function of the gonads (ovaries and testes),
  • lactotropic: they produce prolactin, which is a hormone responsible, among others, for stimulating the production of breast milk.

In the residual intermediate lobe (as well as in the anterior pituitary gland) another, not yet mentioned hormone, melanotropin (MSH) is produced, which influences the activity of pigment cells in the skin.

Pituitary: posterior pituitary hormones

The posterior lobe of the pituitary gland is sometimes referred to as the pituitary gland. Some researchers consider this part of the pituitary gland to be part of the hypothalamus not only because of its origin and connection to this organ, but also because this part of the pituitary gland does not actually produce hormones on its own. Oxytocin (which affects the secretion of breast milk) and vasopressin (an antidiuretic hormone, ADH, which is involved in controlling the body's water balance) are released from the posterior pituitary gland. However, these substances are only stored and then released from the pituitary gland. The production of vasopressin and oxytocin takes place in the hypothalamus, from which these substances are transported to the posterior pituitary gland.

Pituitary gland: hormone secretion mechanism

The pituitary gland plays an extremely important role in controlling the activities of othersendocrine glands, however, the hypothalamus plays the superior role. It is the hypothalamus that secretes the hormones called liberers - these substances stimulate the pituitary gland to release its hormones. The hypothalamus also produces the opposite hormones - statins - which reduce the release of hormones from the pituitary gland.

The secretion of pituitary hormones is influenced not only by the hypothalamus, but also by the endocrine glands controlled by the pituitary. This is done on the basis of the so-called negative feedback loops. For example, a low blood glucose level is a signal that the release of adrenal hormones is increased. When this happens, the hypothalamus releases corticoliberin, which in turn stimulates the pituitary gland to release corticotropin. The last of these hormones stimulates the adrenal glands to produce, among others, glucocorticosteroids (GCS). Increased concentration of GCS in the blood leads not only to the level of metabolic metabolism, but also affects the activity of the hypothalamus and pituitary gland - under physiological conditions, these two tropic organs stop releasing substances that stimulate the adrenal glands. Thanks to the existence of such mechanisms, the body has the ability to maintain homeostasis and properly adjust the release of hormones to the current needs.

Pituitary gland: diseases of the pituitary gland

Considering how many processes the pituitary gland is responsible for, it probably comes as no surprise that dysfunction of its functions can lead to many different disease states. Pathologies can develop both when the pituitary gland produces too little of its own hormones and when the pituitary gland is released in excess.

One of the more common pituitary problems is neoplastic changes. Pituitary tumors are not uncommon - it is estimated that they can account for up to 15% of all brain tumors. Usually these are benign changes, they can either produce some hormone or be without hormonal activity. In the case of hormonally active tumors, the most common of them is prolactinoma, i.e. an adenoma that produces prolactin. There are also other pituitary adenomas, such as those that overproduce growth hormone or those that secrete excessive amounts of corticotropin.

It would seem that adenomas without hormonal activity are less dangerous than the changes that hormones produce. In fact, it turns out that this is not necessarily the case - tumors that do not produce hormones may, for example, grow and interfere with the function of normal pituitary cells, which may lead to a shortage of various hormonestropics and eventually hypopituitarism. Neoplastic lesions developing in the area of ​​the optic crossing may, in turn, put pressure on the elements of the visual pathway, which may cause patients to experience visual disturbances.

Disorders of the pituitary gland can lead to many diseases - so many that it would be difficult to even briefly describe each of them in this study. It remains only to list the most common diseases that are related to the malfunctioning of the pituitary gland, which are:

  • multi-hormonal pituitary insufficiency
  • gigantism
  • acromegaly
  • pituitary dwarfism
  • secondary hypothyroidism or secondary hyperthyroidism
  • Cushing's disease
  • diabetes insipidus
  • empty saddle team
  • Sheehan's band
  • pituitary inflammation
  • syndrome of inappropriate vasopressin secretion (SIADH)

Category:

Anatomy