What is the adenohypophysis?
The adenohypophysis is called the anterior pituitary and is the major part of the pituitary gland. Unlike the neurohypophysis, it is not part of the brain. Thus, the hypophysis, composed of adenohypophysis and neurohypophysis, is not a unified organ. It is only a functional unit of two different proportions.
The adenohypophysis arises from the Rathke pocket, a protuberance of the pharynx. As the fetus grows, this protuberance is pinched off the mouth and develops into the anterior pituitary gland. The pituitary anterior lobe is constructed like a typical endocrine gland. He forms a series of hormones that either act as control hormones or act directly on the organ of success. However, the hormone production of the adenohypophysis is again controlled by releasing or inhibiting hormones of the hypothalamus.
Anatomy & Construction
The adenohypophysis is composed of three parts, the anterior lobe (Pars distalis), the lobe (Pars intermedia) and the funnel lobe (Pars tuberalis). The anterior lobe as the foremost part of the pituitary again contains acidophilic, basophilic and chromophobic cells. These cell differences result from their different colorability by acidic or basic dyes.
For example, the acidophilic cells can be colored red by an acidic dye and the basophilic cells by a basic dye to stain blue or violet, while the chromophobic cells are not stainable. The acidophilic and basophilic cells, unlike the chromophobic cells, are responsible for the production of a number of hormones that perform different functions.
Chromophobic cells include both stem cells and spent acidophilic and basophilic endocrine cells that no longer produce hormones. The lobe (Pars intermedia) is located between the anterior lobe and the neurohypophysis. He is responsible for the production of melanocyte-stimulating hormone (MSH). About the function of the funnel flap, which encompasses the pituitary stalk, is not yet known. The structure of the adenohypophysis makes it an important switching center for controlling hormonal processes in the organism.
Function & Tasks
The adenohypophysis produces both glandotropic (glandular) and non-glutotropic hormones. The glandotropic hormones have important controlling functions. They regulate the hormone production of other hormone glands. The glandotropic hormones formed in the adenohypophysis are TSH (thyroid stimulating hormone), ACTH (adrenocorticotropic hormone), FSH (follicle stimulating hormone) and LH (luteinizing hormone). TSH stimulates hormone production in the thyroid gland and thus influences the energy consumption of the metabolism.
ATCH stimulates the adrenals to produce glucocorticoids, mineral corticosteroids and sex hormones. FSH acts on the gonads and controls the growth of eggs in women and sperm formation in men. Finally, the LH acts on the gonads and is responsible together with the FSH for the maturation and formation of the gametes. Non-steroidal hormones produced in adenohypophysis include STH (somatotropic hormone or somatropin), prolactin and MSH (melanocyte-stimulating hormone or melanotropin).
The STH controls the growth of the organism as so-called growth hormone. In somatropin deficiency dwarfism occurs, while an excess of STH leads to gigantism (hypersomia). In turn, the hormone prolactin controls breast growth and milk production during pregnancy and lactation. The non-steroidal hormone MSH (melatropin) is responsible for the formation of the pigment-forming melanocytes. It also limits the fever reaction and is involved in the control of hunger and sexual excitability. However, the mode of action of the hormones should be considered in the overall context. Thus, the function of the adenohypophysis as part of a complex hormonal system is again controlled by the releasing and inhibiting hormones of the hypothalamus.
By incorrect regulation in the adenohypophysis different hormonal diseases are possible. Since the complex hormone system is precisely matched, a deficiency or excess of a particular hormone can have serious health consequences. There are typical endocrine disorders for every single hormone. For example, TSH regulates thyroid hormone production.
If there is a deficiency of TSH, too little thyroid hormone is formed, which can lead to secondary hypothyroidism. This slows down the metabolism and the physical and mental performance decreases. In addition, it comes to a weight gain. If too much TSH is produced, the thyroid gland is stimulated to produce high levels of thyroid hormone. It comes to hyperthyroidism with their typical symptoms. Disturbances in TSH production can be triggered by adenomas (benign tumors) or autoimmune diseases of the adenohypophysis.
Elevated levels of ACTH result in increased production of cortisol in the body, with the result that Cushing's disease develops with weakening of the immune system and development of a characteristic trunk fatty addiction. Low ACTH levels are often the cause of the so-called Sheehan syndrome with the reduction of many body functions. In addition to hypothalamic dysregulation, the cause of the hormone disorder may be directly related to adenohypophysis.
The non-glutotropic hormone somatropin, in turn, leads to short stature, increased body fat mass with reduced muscle mass and low bone density in the event of a deficiency. Life expectancy is reduced. Overproduction of somatropin causes gigantism. Disorders of the function of the adenohypophysis therefore cause endocrine disorders that can affect the energy and mineral metabolism, growth, milk production, sexual functions and fertility.
Typical & common diseases
- Cushing syndrome
- short stature