- Anterior pituitary or adenohypophysis with a role in the synthesis of the regulatory hormones represented by HGH the growth hormone, PRL prolactin, FSH the follicle stimulating hormone, LH the luteinizing hormone, ACTH the adrenocorticotropic hormone and TSH the thyroid stimulating hormone. These hormones modulate the function of peripheral endocrine glands or act directly on different systems and organs, having a strong impact on metabolism.
- Posterior pituitary or neurohypophysis at the level of which the axonal projections of the hypothalamic magnocellular neurons are found, with a role in the release of vasopressin and oxytocin at the circulatory level.
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Production of pituitary hormones
The hormones synthesized by the anterior pituitary gland are:
- HGH or human growth hormone, also known as somatotropin, it is secreted by the acidophilic cells of the anterior pituitary gland under the regulation of the growth hormone-releasing hormone GHRH and the inhibiting factor for the release of somatotropin SRIF. HGH stimulates RNA production and protein synthesis processes, mobilizes fatty acids from stores and presents transient insulin antagonistic effects.
- Prolactin it is synthesized by the lactotrophic acidophilic cells of the anterior pituitary gland and has a lactogenic and galapoiectic function, determining the appearance of lactation immediately after birth through its action on the mammary glands.
- FSH follicle-stimulating hormone together with LH, it belongs to the category of gonadotropic hormones, having the function of stimulating spermatogenesis in men and the growth and maturation of ovarian follicles in women. The maximum concentration of FSH is recorded in the ovulation stage, but its increase is lower compared to that of LH.
- LH or luteinizing hormone stimulates the growth and good functioning of the gonads (ovaries and testicles) together with FSH. At the level of the ovaries, LH stimulates the growth and maturation of the follicles, supporting the formation and evolution of the corpus luteum and the synthesis of estrogen and progesterone. In men, luteinizing hormone stimulates the activity of testicular Leydig cells (being also called interstitial cell stimulating hormone), testosterone synthesis and sperm maturation.
- ACTH or adrenocorticotropic hormone controls the development and synthesis of glucocorticoid hormones through its action on the fasciculate area of the adrenal glands. The indirect effects of ACTH on carbohydrate, protein and lipid metabolism are due to the action of glucocorticoid hormones on the body.
- TSH or thyroid stimulating hormone also known as thyrotropin, it is synthesized by the basophilic cells of the anterior pituitary gland under the influence of the TSH-releasing hormone produced by the hypothalamus. The TSH has the role of stimulating the synthesis and proliferation rate of the thyroid hormones represented by thyroxine T4 and triiodothyronine T3, having numerous implications at the level of metabolism. TSH is a hormone with diurnal variations, whose maximum serum concentration is recorded around 11 p.m.
At the level of the posterior pituitary gland or the neurohypophysis, the synthesis of:
- Vasopressin or antidiuretic hormone it is a hormone synthesized at the level of the supraoptic and paraventricular nuclei, which, once it reaches the systemic circulation, acts on the collecting tubes, causing an increase in water permeability at their level. Vasopressin synthesis is regulated by hypothalamic osmoreceptors and baroreceptors at the level of large blood vessels, serum concentrations of the antidiuretic hormone being directly proportional to osmolality (the osmotic pressure of a solution expressed in mOsm per kilogram of water).
- Oxytocin is a neurohormone synthesized by the hypothalamus and stored in the posterior pituitary gland, which regulates uterine contractions during labor and initiates lactation immediately after birth. In addition, oxytocin promotes growth and healing processes, generates romantic attachment, contributes to the development of maternal behavior and facilitates the establishment of bonds at the social level.
Diseases of the pituitary gland
Pituitary pathologies that appear as a result of a tumors, trauma, inflammation or infection at this level, it generates hormonal disturbances that can be manifested by:
- Central diabetes insipidus (antidiuretic hormone deficiency)
- Gigantism and acromegaly (due to the accelerated synthesis of growth hormone)
- Hypothyroidism (TSH deficiency)
- Hiperpituitarism
- Hypopituitarism.
Pituitary adenoma
Pituitary gland adenoma is a benign pituitary tumor that represents between 5 and 8% of all intracranial tumors. Functional pituitary adenomas represent benign tumors capable of hormone synthesis (prolactin, growth hormone, ACTH and TSH) which are accompanied by clinical manifestations due to the release into the circulation of excessive amounts of the synthesized hormone.
Non-functional pituitary adenomas usually associate clinical manifestations due to the compression syndrome represented by:
- Loss of vision (in case of pressure exerted by the tumor mass on the optic chiasm)
- Pituitary insufficiency (compression of the pituitary gland with the suppression of its secretory function).
Pituitary insufficiency
Depending on the extension of the pathological process at the level of the pituitary gland, pituitary insufficiency can be classified as follows:
- Monotrophic pituitary insufficiency that develops with the damage of a single type of hormone (gonadotropic insufficiency).
- Bitropic pituitary insufficiency that associates damage at the level of 2 hormonal lines.
- Panhypopituitarism that involves affecting the entire hormonal synthesis.
Sheehan syndrome
Sheehan’s syndrome is a particular type of pituitary insufficiency due to hypoxic lesions of the pituitary gland that occur during a complicated birth that associates hypertension, shock and significant hemorrhage.
Pituitary necrosis and insufficiency occur in the context of significant blood loss during birth that reduces the irrigation of the hypothalamus and pituitary gland.
This type of injury can also occur in men, being caused by diabetes, infection with Koch’s bacillus (tuberculosis) or Treponema pale (the etiological agent of syphilis), mycosis or brucellosis.
Diagnosis of hormonal disorders caused by the pituitary gland
The diagnosis of hormonal disorders due to pituitary pathologies is established by the endocrinologist through the anamnesis, the patient’s clinical examination and laboratory and imaging investigations.
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Realization of the hormonal profile (determining the serum values of certain hormones) is indicated by the endocrinologist according to the clinical manifestations of the patient and requires the collection of peripheral venous blood, depending on the circadian/monthly rhythm of hormone secretion.
Imaging explorations currently used for the diagnosis of pituitary gland disorders are represented by Turkish radiography and pituitary MRIwhile visual campimetry and fundoscopy they can indicate the existence of a possible pituitary tumor formation.
Treatment of hormonal disorders caused by the pituitary gland
The treatment of hormonal disorders associated with pituitary pathologies is carried out in accordance with the recommendations of the endocrinologist and may involve a neurosurgical intervention or radiotherapy in the case of pituitary adenomas or hormone replacement treatment. It is important for the patient to comply with the recommendations of the endocrinologist regarding the performance of dynamic (serial) hormonal evaluations and regular medical visits, because substitution treatments may require periodic adjustment, according to the particularities of each individual case.
References:
- Autoimmune Pituitary Disease: New Concepts With Clinical ImplicationsMasaaki Yamamoto, Genzo Iguchi, Hironori Bando, Keitaro Kanie, Ryoko Hidaka-Takeno, Hidenori Fukuoka, Yutaka Takahashi | Endocrine Reviews
- Diagnosis and Treatment of Pituitary DiseaseIlan Shimon; Shlomo Melmed
- Pituitary disease: presentation, diagnosis, and managementA. Levy
- Update in Pituitary DiseaseThe Journal of Clinical Endocrinology & Metabolism, Shlomo Melmed
2024-01-24 23:01:55
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