An Analysis Of The Pituitary Gland

We know that the human growth hormones start from the pituitary gland in the front side area. Let’s do a little more analysis and research on the gland itself.

From Wikipedia HERE

In vertebrate anatomy the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 grams (0.018 oz) in humans. It is not a part of the brain. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity (sella turcica) covered by a duralfold (diaphragma sellae). The pituitary is functionally connected to the hypothalamus by the median eminence via a small tube called the infundibular stem (Pituitary stalk). The pituitary fossa, in which the pituitary gland sits, is situated in the sphenoid bone in the middle cranial fossa at the base of the brain. The pituitary gland secretes nine hormones that regulate homeostasis.

Sections

The pituitary gland consists of two components: the anterior pituitary (or adenohypophysis) and the posterior pituitary (or neurohypophysis), and is functionally linked to the hypothalamus by the pituitary stalk (also named the “infundibular stem”, or simply the “infundibulum”). It is from the hypothalamus that hypothalamic tropic factors are released to descend down the pituitary stalk to the pituitary gland where they stimulate the release of pituitary hormones. While the pituitary gland is known as the ‘master’ endocrine gland, both of the lobes are under the control of the hypothalamus; the anterior pituitary receives its signals from the parvocellular neurons and the posterior pituitary receives its signals from magnocellular neurons.

Anterior pituitary (Adenohypophysis)

The anterior pituitary synthesizes and secretes the following important endocrine hormones:

Somatotrophins:

  • Growth hormone (also referred to as ‘Human Growth Hormone’, ‘HGH’ or ‘GH’ or somatotropin), released under influence of hypothalamic Growth Hormone-Releasing Hormone (GHRH); inhibited by hypothalamic Somatostatin

Thyrotrophins:

  • Thyroid-stimulating hormone (TSH), released under influence of hypothalamic Thyrotropin-Releasing Hormone (TRH)

Corticotropins:

  • Adrenocorticotropic hormone (ACTH), released under influence of hypothalamic Corticotropin-Releasing Hormone (CRH)
  • Beta-endorphin, released under influence of hypothalamic Corticotropin-Releasing Hormone (CRH)[3]

Lactotrophins:

  • Prolactin (PRL), also known as ‘Luteotropic’ hormone (LTH), whose release is inconsistently stimulated by hypothalamic TRH, oxytocin, vasopressin, vasoactive intestinal peptide, angiotensin II, neuropeptide Y, galanin, substance P, bombesin-like peptides (gastrin-releasing peptide, neuromedin B and C), and neurotensin, and inhibited by hypothalamic dopamine.[4]

Gonadotropins:

  • Luteinizing hormone (also referred to as ‘Lutropin’ or ‘LH’ or, in males, ‘Interstitial Cell-Stimulating Hormone’ (ICSH))
  • Follicle-stimulating hormone (FSH), both released under influence of Gonadotropin-Releasing Hormone (GnRH)

Melanotrophins

  • Melanocyte–stimulating hormones (MSHs) or “intermedins,” as these are released by the pars intermedia, which is “the middle part”; adjacent to the posterior pituitary lobe, pars intermedia is a specific part developed from the anterior pituitary lobe.

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

The anterior pituitary is divided into anatomical regions known as the pars tuberalis, pars intermedia, and pars distalis. It develops from a depression in the dorsal wall of the pharynx (stomodial part) known as Rathke’s pouch.

Posterior pituitary (Neurohypophysis)

The posterior pituitary stores and secretes the following important endocrine hormones:

Magnocellular Neurons:

  • Oxytocin, most of which is released from the paraventricular nucleus in the hypothalamus
  • Antidiuretic hormone (ADH, also known as vasopressin and AVP, arginine vasopressin), the majority of which is released from the supraoptic nucleus in the hypothalamus

Oxytocin is one of the few hormones to create a positive feedback loop. For example, uterine contractions stimulate the release of oxytocin from the posterior pituitary, which, in turn, increases uterine contractions. This positive feedback loop continues throughout labor.

Intermediate lobe

Although rudimentary in humans (and often considered part of the anterior pituitary), the intermediate lobe located between the anterior and posterior pituitary is important to many animals. For instance, in fish, it is believed to control physiological color change. 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 (imprecisely) attributed to the anterior pituitary.

Variations among vertebrates

The pituitary gland is found in all vertebrates, but its structure varies between different groups.

The division of the pituitary described above is typical of mammals, and is also true, to varying degrees, of all tetrapods. However, only in mammals does the posterior pituitary have a compact shape. Inlungfishes, it is a relatively flat sheet of tissue lying above the anterior pituitary, and, in amphibians, reptiles, and birds, it becomes increasingly well developed. The intermediate lobe is, in general, not well developed in tetrapods, and is entirely absent in birds.[5]

Apart from lungfishes, the structure of the pituitary in fish is generally different from that in tetrapods. In general, the intermediate lobe tends to be well developed, and may equal the remainder of the anterior pituitary in size. The posterior lobe typically forms a sheet of tissue at the base of the pituitary stalk, and in most cases sends irregular finger-like projection into the tissue of the anterior pituitary, which lies directly beneath it. The anterior pituitary is typically divided into two regions, a more anterior rostral portion and a posterior proximal portion, but the boundary between the two is often not clearly marked. Inelasmobranchs there is an additional, ventral lobe beneath the anterior pituitary proper.[5]

The arrangement in lampreys, which are among the most primitive of all fish, may indicate how the pituitary originally evolved in ancestral vertebrates. Here, the posterior pituitary is a simple flat sheet of tissue at the base of the brain, and there is no pituitary stalk. Rathke’s pouch remains open to the outside, close to the nasal openings. Closely associated with the pouch are three distinct clusters of glandular tissue, corresponding to the intermediate lobe, and the rostral and proximal portions of the anterior pituitary. These various parts are separated by meningial membranes, suggesting that the pituitary of other vertebrates may have formed from the fusion of a pair of separate, but associated, glands.[5]

Most armadillo also possess a urophysis, a neural secretory gland very similar in form to the posterior pituitary, but located in the tail and associated with the spinal cord. This may have a function inosmoregulation.[5]

There is an analogous structure in the octopus brain.[6

From the Department Of Neurological Surgery at the University of Pittburgh website HERE

What is the Pituitary Gland?
The pituitary gland is a pea-sized gland located at the base of the skull between the optic nerves. The pituitary gland secretes hormones. Hormones are chemicals that travel through our blood stream. The pituitary is sometimes referred to as the “master gland” as it controls hormone functions such as our temperature, thyroid activity, growth during childhood, urine production, testosterone production in males and ovulation and estrogen production in females. In effect the gland functions as our thermostat that controls all other glands that are responsible for hormone secretion. The gland is a critical part of our ability to respond to the environment most often without our knowledge.

The pituitary gland actually functions as two separate compartments an anterior portion (adenohypohysis-hormone producing) and the posterior gland (neurohypophysis). The anterior gland actually is made of separate collection of individual cells that act as functional units (it is useful to consider them as individual factories) that are dedicated to produce a specific regulatory hormone messenger or factor. These factors are secreted in response to the outside environment and the internal bodily responses to this environment. These pituitary factors then travel through a rich blood work network into the blood stream and eventually reach their specific target gland. They then stimulate the target gland to produce the appropriate type and amount of hormone so the body can respond to the environment correctly.

Similar to the cortisol factory there are additional factories:

  • Growth Hormone
  • Prolactin
  • Gonadotropin (“sex hormones”)
  • Thyroid

These five axes (factories) function as the anterior pituitary gland neuroendocrine unit. If any one of these factories become excited and start to overproduce their respective hormonal factor the net result is excess production of the final hormone product. So in the above example, if the cortisol cells (corticotrophs) lose their ability to respond to the normal stimuli from the environment and hypothalamus and develop their own independent, uncontrolled autonomous secretion they will produce more cortisol than the body requires. In return the adrenal gland will be over stimulated and secrete unregulated and unneeded catecholomines (stress chemicals). The net result is excess production of these important chemicals that raise the blood pressure and drive the heart in order to respond to stress when needed and can cause the body and internal organs to be stressed when there is no need. The consequences of overdriving the internal organs of the body can be life threatening. Often these cells that overproduce their respective hormone will clump together within a given area of the pituitary gland creating a true factory of over production – pituitary tumor.

In addition to these five factories (cell lines) that produce hormones the anterior pituitary gland also contains remnants of the parent cells from which each of these individual cells came from. Specifically as the pituitary gland was formed the anterior gland contained a parent cell (pituicyte) which if you will was a parent cell. During embryological development this parent cells grew and matured into a series of daughter cells. Each of these daughter cells differentiated or learned to secrete a specific type of hormone eventually resulting in one of the five factory cells. In about 20% of the cases in fact the parent cell (which has not yet learned to secrete anything) grows excessively creating a collection or clump—pituitary tumor. This clump can grow and in the process create pressure on adjacent structures. Therefore these nonsecreting tumors create a problem for the patient not from excess hormone production but rather because of pressure on adjacent structures.

What are the adjacent structures?

If the pressure is exerted on the other members of the pituitary gland directly it impairs their ability to secrete their specific hormone – pituitary dysfunction. Among the most sensitive factories are the sex hormones (gonadotropins). If the pituitary tumor grows sideways (fat tumor) it will compress the cavernous sinus. This structure is an important cave located on either side of the gland that is continues a channel for blood to drain out of the brain, the carotid artery to supply the brain, and the cranial nerve that move the eyes. Fortunately, dysfunction of these critical structures is a rare and late event in most cases. However it is more likely that the gland will grow tall or upward (tall tumor). Often it will extend out of the bony structure that houses the pituitary gland (sella – named after the Turkish saddle). It will then grow through the thin “saran wrap” – like membrane (diaghrama) that separates the pituitary fossa or sella from the brain. It will then start to grow upward and start to push on the junction of the optic nerves where they cross (optic chiasm). When this happens the vision becomes compromised. The pattern of vision loss is a reflection of the compression at the site of crossing and so the patient develops blind spots along both temple regions.

Both tumors that secrete hormones (functional tumors) and tumors that do not (non-functional tumors) can create this pressure or mass effect. More often it is these nonfunctional tumors that present with visual loss. In order for visual loss to occur the tumor has to be larger and grown through the confines of the sella and upward to the optic chiasm. These tumors are generally larger. The functional tumors often present when they are smaller because they have created a syndrome of excess production that prompts the patient to get help often before the vision is compressed.

From the website Cancer.Net HERE ….

About the pituitary gland

The pituitary gland is a small gland located near the brain. This gland is often referred to as the “master endocrine gland” because it releases hormones that affect many bodily functions. The pituitary gland is controlled by the hypothalamus, a small structure also near the brain that is connected to the pituitary gland. A pituitary gland has two lobes, the anterior (front) and the posterior (back), and each lobe is responsible for releasing specific hormones. These different hormones include:

Anterior pituitary lobe hormones

  • Thyroid stimulating hormone (TSH) stimulates the thyroid gland, which helps regulate the body’s metabolism
  • Adrenocorticotrophic hormone (ACTH) controls the hormones released by the adrenal gland that support blood pressure, metabolism, and the body’s response to stress
  • Gonadotropins (Follicle stimulating hormone or FSH and Luteinizing hormone or LH) stimulate production of sperm in a man’s testicles or eggs in a woman’s ovaries and regulate a woman’s menstrual cycle
  • Growth hormone promotes growth of the long bones in the arms and legs, thickens the skull and bones of the spine, and causes the tissue over the bones to thicken
  • Prolactin stimulates milk production in women after childbirth
  • Lipotropin stimulates the movement of fat from the body to the bloodstream
  • Melanocyte stimulating hormone (MSH) regulates the production of melanin, the pigment in skin

Posterior pituitary lobe hormones

  • Oxytocin stimulates contraction of the uterus during childbirth and the flow of milk during breastfeeding
  • Antidiuretic hormone (called vasopressin) increases reabsorption of water by the kidneys and allows a person to stay hydrated

Tumors in the pituitary gland

When normal cells change and grow uncontrollably, they can form a mass called a tumor. A pituitary gland tumor can be benign (noncancerous and located only in the pituitary gland) or malignant (cancerous, meaning it can spread to other parts of the body). Most often, pituitary gland tumors are noncancerous growths and are called pituitary adenomas. However, a pituitary gland tumor can occasionally act like a cancerous tumor by growing into nearby tissue and structures, or rarely, spreading to other parts of the body.

Pituitary gland tumors are NOT brain tumors, as the pituitary gland is located under and is separate from the brain. However, a tumor in this gland can be very serious because a pituitary gland that doesn’t work can cause problems with other organs. The tumor can also press on nearby structures, such as the optic nerves, impairing a person’s sight.

Me: The big thing for us height seekers to note is that the Pituitary gland is not actually a part of the brain but actually the lower part of the hypothalamus and is connected by a small tube called the infundibular stem (Pituitary stalk). It releases 9 major hormones that regulate the body’s homeostasis. There is two parts to it although the truth is that the gland is actually a combination of different functioning cells. The HGH is just one of the 9 hormones being released. The hormone release is regulated by the either the growth hormone releasing hormone (GHRH) or the growth hormone inhibiting hormone (GHIH) which is released by the hypothalamus. Hypothalamic hormones are secreted to the anterior lobe by way of a special capillary system, called thehypothalamic-hypophysial portal system. The pituitary giants we get are usually from the clumping of certain cells in the pituitary coming together which is usually benign.

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