What is the function of the Pituitary Gland?

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The Pituitary gland is a pea-sized endocrine (hormone-producing) gland weighing about 0.5 g situated at the bottom of the skull sandwiched between the optic nerves, in humans. The pituitary gland secretes hormones. Hormones are chemicals that travel through the blood stream. The pituitary gland is every now and then called the "master" gland of the endocrine system, as it controls the functions of the other endocrine glands, such as the temperature, thyroid activity, growth during early days of birth, urine production, testosterone production in males and ovulation and estrogen production in females. The pituitary is functionally connected to the hypothalamus, a part of the brain that has a number of small nuclei with a variety of functions. The pituitary fossa, in which the pituitary gland rests, is located in the sphenoid bone, an unpaired bone situated at the base of the brain. The pituitary gland secretes nine hormones that regulate homeostasis, the property of a system, either open or closed, that regulates its internal environment and tends to maintain a stable, constant condition.

Why is pituitary gland vital?

The pituitary gland is vital as it conveys messages from the brain by means of a gland called the hypothalamus and make use these messages to manufacture hormones that affect numerous parts of the body and activating all the other hormone-producing glands to generate their own hormones. This is the reason why it is called the “Master gland”.

What are the parts of pituitary gland and the hormones they secrete?

The pituitary gland has 3 parts:

I. The Anterior pituitary (or adenohypophysis): The Anterior (or front) pituitary produces hormones that affect the breasts, adrenals, thyroid, ovaries and testes, in addition to several other hormones. The anterior pituitary receives its signals from the ‘parvocellular neurons’ in the brain. The anterior pituitary synthesizes and secretes the vital endocrine hormones, such as:

• Adrenocorticotropic hormone (ACTH), in order to activate the adrenal glands. Cortisol, a so-called "stress hormone" is very important to human survival. It helps to maintain blood pressure and blood glucose levels.
• Thyroid-stimulating hormone (TSH), in order to stimulate the thyroid gland
• Follicle-stimulating hormone (FSH), to stimulate the ovaries in women and testes in men and to stimulate the ovaries to enable ovulation in women.
• Luteinizing hormone (LH), to stimulate the ovaries or testes
• Growth hormone (GH) in order to help in the growth of human beings. GH stimulates growth in childhood and is vital for maintaining a healthy body composition and happiness in adults. In adults, it is important for maintaining muscle mass and bone mass. It also affects fat distribution in the body.
• Hormone Releasing Hormone (GHRH), to release hormones.
• Prolactin, to activate milk production after child birth in women. It also affects sex hormone levels from ovaries in women and from testes in men.

These hormones are released from the anterior pituitary under the influence of the hypothalamus. Hypothalamic hormones are secreted to the anterior lobe through an unique way of a special capillary system, called the hypothalamic-hypophysial portal system.

II. Intermediate lobe: There exist an intermediate lobe in several animals, but is basic in humans. For example, it is assumed to control physiological color change in fishes. In adult humans, it is just a thin layer of cells between the anterior and posterior pituitary. The intermediate lobe produces melanocyte-stimulating hormone (MSH), although this function is often vaguely credited to the anterior pituitary. MSH is secreted to control skin pigmentation.

III. The posterior pituitary (or neurohypophysis): The main glands affected by the posterior (or rear) pituitary are the kidneys. The posterior pituitary receives its signals from ‘magnocellular neurons’ in the brain. The posterior pituitary gland stores and releases hormones, such as:

• Oxytocin, plays a major role in the human brain system since it is one of the few hormones to produce a positive reaction ring. For instance, uterine contractions rouse the release of oxytocin from the posterior pituitary, which, sequentially, increases uterine contractions. This positive reaction ring continues all over the labor process in women. Oxytocin stimulates milk production in women too.
•  Antidiuretic hormone (ADH), in order to increase absorption of water into the blood by the kidneys. ADH is also called as vasopressin. It regulates water balance in the body. If this hormone is not released correctly, it can lead to scanty hormone (called diabetes insipidus), or too much hormone (called syndrome of inappropriate ADH). Both of these conditions affect the kidneys. Diabetes insipidus is different from the more famous diabetes mellitus (including type 1 and type 2 diabetes), which affects the levels of glucose in human bodies.
  
   

Both anterior and posterior glands are functionally linked to the hypothalamus by the pituitary stalk. It is from the hypothalamus that hypothalamic tropic factors are discharged to move down the pituitary stalk to the pituitary gland where they rouse the discharge of pituitary hormones. Both of the lobes are controlled by the hypothalamus.

What are the other major functions of hormones secreted by pituitary gland in humans?

Hormones secreted from the pituitary gland aid controls the body processes, such as:

• Blood pressure
• Physical growth in human beings
• A few stages of pregnancy and childbirth including stimulation of uterine contractions during childbirth.
• Breast milk production
• Sex organ functions in both men and women
• Thyroid gland function
• The change of food into energy (metabolism)
• Water and osmolarity regulation in the body
• Water balance by means of the control of reabsorption of water by the kidneys
• Temperature regulation.

How does the pituitary gland work?

A specialized cell transmitting nerve impulses called the ‘neurons’ transmit messages concerning the production of hormones between the pituitary gland and the hypothalamus. Together they are situated at the base of the brain, snuggled in a rounded part of bone, vigilantly secluded. They are linked by a bunch of neurons called the ‘infundibulum’. In concert, they work to regulate all the hormones that circulate in the bloodstream, controlling things like growth and hair pigmentation. Hormones are the long-distance messengers that can notify cells when to become active or stay inactive. The pituitary gland controls the thyroid, adrenal glands, ovaries and testes, in spite of its tiny size.

What are pituitary gland tumors?

The major cause of pituitary disorders is ‘pituitary gland tumors’. The pituitary gland is made of a number of cell types. At times, these cells grow too much or produce small growths. These growths are called pituitary tumors, and they are fairly common in adults. These are not brain tumors and are not a form of cancer. Actually, cancerous tumors of this kind are extremely unusual. Pituitary tumors, on the other hand, can obstruct with the normal formation and release of hormones.

What are the types of pitutray tumor?

There are two types of tumors exist:

• Secretory: Secretory tumors produce excessive hormone, creating a disproportion of proper hormones in the body.
• Non-secretory: Non-secretory tumors cause problems due to their large size or because they interfere with normal function of the pituitary gland.

What do these pitutary tumors cause in humans?

The various concerns caused by pituitary tumors fall into three major groups:

• Hypersecretion: Excessive hormone secreted into the body is normally caused by a secretory pituitary gland tumor. Many secretory tumors produce excessive prolactin. Other tumors may affect the adrenal glands, making excess hormones that rouse them and create a hormone disproportion. Tumors also can produce surplus growth hormone or excessive of the hormone that rouses the thyroid gland leading to overproduction of thyroid hormones.
• Hyposecretion: Insufficient hormones are secreted into the body due to a non-secretory pituitary gland tumor, which interferes with the skill of the normal pituitary gland to create hormones. Hyposecretion can also occur with surgery or the radiation of a pituitary gland tumor.
• Tumor mass effects: When a pituitary gland tumor grows and pushes against the normal pituitary gland or other areas in the brain, it may cause headaches, vision problems, or other health effects related to hyposecretion. Tumor mass effects can be seen in any kind of pituitary tumor that grows very large. Injuries, certain medications, and other conditions can also affect the pituitary gland. Loss of normal pituitary function also has been accounted after major head trauma.

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