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.
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