Information about Pituitary endocrine gland and its functions


Do you know which gland is known as master gland in our body? In this article, you will find a detail explanation of pituitary gland. You will get information about its location, structure, different hormones secreted by it, etc.

Introduction and location

The pituitary gland has the regulatory influence on almost all the endocrine gland of the body, hence pituitary gland is regarded as master gland. The pituitary gland also forms a link between the nervous and endocrine system and maintains functional coordination between the two. Name pituitary was given by Vesalius. Pituitary develops from ectoderm of the embryo.
pituitary gland(Note: Image curtsey: https://en.wikipedia.org)

The pituitary gland is located on the ventral side of the brain in the region of diencephalon just behind the optic chiasma where the optic nerves cross each other. Pituitary gland lies in the cavity of the sphenoid bone, called sella turcica on the floor of the cranial cavity. The pituitary gland is a small, reddish-grey, rounded unpaired body, about the size of large pea weighing about 0.5 gm in man and usually becomes much larger in the pregnant woman. The pituitary gland hangs below the hypothalamus by a stalk called infundibulum> Hypothalamus is a part of the brain.

Structure of Pituitary gland

The pituitary gland has three different parts:
  1. Anterior lobe
  2. Intermediate lobe or Adenohypophysis

  3. Posterior lobe or Neurohypophysis


The anterior lobe is a compact and highly vascular part. The anterior lobe is connected to the hypothalamus by hypophysial portal vessels. The anterior lobe and intermediate lobe are together known as adenohypophysis while the posterior one is known as neurohypophysis.

Adenohypophysis

Adenohypophysis is the largest compact and vascular part of the pituitary in all vertebrates. Adenohypophysis develops as an outgrowth of the pharynx, called Rathke's pouch and is made up of three parts: Pars distalis, pars tuberalis, and Pars intermedia. Pars distalis is the largest part of the adenohypophysis. Pars distalis forms about 75 percent of the gland.

Neurohypophysis

Neurohypophysis is the posterior part of the pituitary gland which forms the 1/4th portion of it. Neurohypophysis is connected to the brain with the help of infundibular stalk. The hormone of the posterior lobe is synthesized in the hypothalamus, they are carried along nerves to the posterior lobe which stores and secretes them into the blood.

Hormones of Adenohypophysis


The adenohypophysis releases six hormones which control the activities of various other endocrine glands also.

  1. Somatotrophic hormone (STH) or Growth Hormone (GH)


  2. GH acts directly on almost all tissues of the body to regulate general body growth. GH also controls protein, fat and carbohydrate metabolism to a great extent.

    Hyposecretion of GH

    The hyposecretion of growth hormone causes following diseases:

    • Dwarfism
    • : Deficiency of GH during childhood causes dwarfism. This type of dwarfness in young ones is described as ateleilosis and the dwarfs are called midgets.
    • Pituitary myxodema
    • : Hyposecretion in adults produces symptoms like hypothyroidism from hypoactivity of the pituitary.

    Hypersecretion of GH

    The hypersecretion of growth hormone causes following diseases:

    • Gigantism
    • : Hypersecretion or excessive secretion of growth hormone causes gigantism in young in which general overgrowth of the skeleton resulting in an individual of 7 to 8 feet or more in height. The limbs are generally disproportionately long.
    • Acromegaly
    • : Hypersecretion of GH cause acromegaly in adults. in this disease a characteristic enlargement or overgrowth of the bones of the hands feet and in particular the jaws, cheeks, and face take place. There is also an excessive growth of fibrous tissue resulting in the thickened nose, lips eyelids, and broadened fingertips.

  3. Lactogenic Luteotrophic Hormone (LTH)


  4. It is also known as the Luteotrophic hormone or Mammotrophic hormone. Nicol and Bern called this hormone as "Jack of all trades" because of more than seventy-five different hormonal activities performed by it. this hormone has the following main functions:

    • LTH stimulates the production of milk in the mammary glands of mammals.

    • LTH stimulates the development of corpus luteum.

    • LTH during pregnancy helps in maintaining the functional state of corpus luteum.

    • LTH encourages maternal instinct and behaviour which are important for the survival of young ones.


    Hyposecretion of LTH: Size of mammary glands is reduced. Milk is also not produced.
    Hypersecretion of LTH: More milk is produced in mammary glands. The glands also become large sized. Lactation may occur ever without childbirth.

  5. Adrenocorticotropic Hormone (ACTH)


  6. The functions of ACTHare as follows:

    • ACTH stimulates adrenal cortex to secrete all its normal hormones at an increased rate. more specifically, ACTH induces hypertrophy of the zona fasciculata and causes the secretion of glucocorticoids.

    • ACTH stimulates glucocorticoid secretion from adrenal cortex to meet stressful stimuli.


  7. Thyrotrophic or Thyroid Stimulating Hormone (TSH)


  8. The primary function of TSH is to regulate the growth of the thyroid gland and its secretory activity. Thyrotrophin promotes accumulation of iodine and increases the quantity of intracellular colloid in the thyroid epithelial cells and induces the liberation of thyroxine hormone.

  9. Gonadotrophins or Gonadotrophic Hormone (GTH)


  10. These are two gonadotrophins secreted by basophils of adenohypophysis which control various activities of gonads:

    • Follicle Stimulating Hormone (FSH)
    • : In females, FSH stimulates the growth of the Graafian follicle and secretion of estrogen by follicle cells. In male FSH stimulates the process of spermatogenesis and sperm formation and follicle formation in the ovaries of females. Due to its action on both the male and female gametes, FSH is also referred as gameto-kintetic factor.
    • Luteinizing Hormone (LH)
    • : In female LH brings about ovulation, i.e. release of the mature ovum from the ovary. LH works with FSH and both are responsible for the development of corpus luteum that in turn secretes progesterone which maintains pregnancy. In the male, LH stimulates the interstitial cells or cells od Leyding of testes to secrete testosterone or male sex hormone, hence in males, this hormone is known as ICSH.

    Hypoactivity of GTH: In females, if Gonadotrophic Hormones are secreted in insufficient quantity, size of the ovary is reduced. Follicles are destroyed. Uterus and vagina are also deformed. In males also the condition leads to the collapse of the sexual reproductive system. Testes are diminished in size. The testes remain inside the abdomen if the deficiency of the hormone occurs in fetus stage. Suc males are called cryptorchid.
    Hypersecretion of GTH : Over secretion gonadotrophic hormones leads to sexual prematurity.

  11. melanocyte stimulating hormone (MSH)


  12. MSH is secreted by the intermediate lobe of the pituitary. MSH influences chromatophore system in fishes, amphibians, etc. The role of MSH in mammals is not yet very clear. In man, MSH hormone controls the changes in the colour of skin.

Hormones of Posterior Lobe Neurohypophysis


The Neurohypophysis or posterior lobe of pituitary releases the following two peptide hormones. Both of these hormones are synthesized in the hypothalamus and are carried to the neurohypophysis along with nerve fibers where they are stored and then released into the blood.

  1. Antidiuretic (ADH) or Vasopressin Hormone


  2. ADH plays an important role in osmoregulation. ADH is released in response to stress and dehydration. When the body fluids become highly concentrated, the impulses are transmitted to the posterior lobe and ADH is released by way of blood. ADH reaches kidneys where it increases the permeability of the distal tubules and collecting tubules to water, as a result, most of the water is reabsorbed from the urine. ADH is inactivated primarily in the kidney and liver and then excreted along with urine. ADH also controls blood pressure. Alcohol inhibits the ADH secretion.
  3. Oxytocin


  4. Oxytocin is an important uterus contracting hormone at the time of childbirth. Oxytocin also increases the motility of uterus during coitus thereby promoting fertilization. Pitocin also acts on mammary glands and helps in the milk ejection by initiating the contraction of smooth muscles and the myoepithelial cells which encircle the alveoli and cause expulsion of milk.

So it is clear that Pituitary gland controls all other endocrine glands of our body, hence Pituitary gland is called master gland of our body. The pituitary gland is also referred as Piyush gland. The removal of the pituitary gland is called hypophysectomy.


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Comments

Author: Natarajan07 Jan 2018 Member Level: Diamond   Points : 5

This chief endocrine gland, although very small, control other glands like gonads, thyroid, mammary glands in breast and the adrenal glands.
Like any other organ in the human body, the pituitary gland is also affected by diseases or tumours. Often these tumors are benign, a simple way to study them is by classifying tumours that are functional (hypo or hyper) and nonfunctional (produce symptoms by compression the gland in the relatively small space of sella turcica).

Pituitary apoplexy is a serious condition that presents with a headache, confusion, seizures or a sudden change in vision often due to an enlarging adenoma or pituitary tumors or in some cases wherein there is major blood loss (related to childbirth or accidents) the blood supply to the pituitary gets compromised. These disorders need the expert services of a specialist endocrinologist and at times a Neurosurgeon with experience in skull-based surgery.



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