The Pituitary Gland and Hypothlamus
The pituitary gland and hypothalamus are located in the brain. The pituitary is functionally related to, physically connected to, and, along with the target organs, controlled by the hypothalmus. The pituitary is shown as yellow or light blue depending on the picture below. The hypothalamus is depicted in green.
The hypothalamus and pituitary gland may play a role in many of the signs and symptoms associated with neurodegenerative diseases such as Alzheimer's, Parkinson's and multiple sclerosis. Interestingly, autoimmune-inflammatory condtions such as rheumatoid and psoriatic arthritis are, likewise, often associated with signs and symptoms that suggest possible hypothalamus and pituitary dysfunction, as are certain inherited connective tissue disorders such as Ehlers-Danlos syndrome. In this regard, they may all share similar causes of hypothalamic-pituitary dysfunction related to obstruction of cerebrospinal fluid (CSF) flow. Signs and symptoms of hypothalamus or pituitary problems can include: heat intolerance, sensitivity to cold, disruption in sleep cycles, short shallow breathing, fatigue, cog fog, decreased memory, irritability, mood swings, muscle cramps, increased urination and constipation.
In humans the pituitary gland or hypophysis has two basic parts called the anterior and posterior pituitary. The anterior part of the pituitary, adenohypophysis, is regulated by the hypothalamus and by a negative feedback from target organs. The target organs are the adrenals, liver, bone, thyroid, and gonads. It produces and secretes adrenocorticotropin, beta endorphin, thyroid-stimulating, follicle stimulating, luteinizing, prolactin and growth hormone. The posterior pituitary gland (technically not a gland) also known as neurohypophysis is actually a collection of nerve projections that come from control centers in the hypothalamus. In contrast to the anterior pituitary, the posterior pituitary stores and secretes oxytocin and antidiuretic hormone (also known as vasopressin and arginine vasopressin), which are produced in the hypothalamus.
The pituitary gland is part of the endocrine system of the body. The endocrine system secretes hormones directly into the bloodstream, unlike the exocrine system that uses ducts. The endocrine system is similar to the nervous system in that they are both informational signal systems and the pituitary and hypothalamus are part of the brain, but the similarities end there. The endrocine system signals are slow to initiate and produce a relatively prolonged respone. The nervous system sends information quickly and it's responses are short-lived. Most of the nervous system uses neurotransmitters to relay signals and control systems in the brain and body. In contrast the endocrine system use hormones that travel through the blood stream to reach and regulate various systems.
The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system responsible for maintaining homeostasis such as: hunger, appetite, temperature regulation, sleep cycles, reproduction, stress and water balance. In some species, it initiates and controls hibernation. The hypothalamus also synthesizes and secretes certain neurohormones often called hypothalamic releasing hormones that stimulate or inhibit the secretion of pituitary hormones.
Location of the Pituitary in the Brain - The Sella Turcica
The pituitary gland is contained in a small separate subcompartment in the base of the skull called the sella turcica. Sella turcica means Turkish saddle. They were probably named after the deep saddles used on camels not horses. There are many different styles of camel saddles. The picture below on the left is an example of a Tuareg camel saddle.
The sella turcica is part of the sphenoid bone in the base of the skull. The sphenoid sinus and sella turcica portion of the sphenoid bone are shown in yellow in the drawing below. The sphenoid sinus is part of the air chambers called sinuses located in the face and base of the skull.
There are two horn-like projections at the rear of the sella turcica called the clinoid processes. The clinoid processes are poles for the attachment of the diaphrama sella. The diaphrama sellae covers the sella turcica compartment and separates it from the rest of the cranial vault above it. The diaphrama sellae is made from the tough outer covering of the brain called the dura mater. It is similar to the tentorium cerebelli, which covers and separates the posterior fossa and cerebellum from the rest of the brain. It is located in the cup-like structure in the yellow colored bone below.
Hormones of the Pituitary
To understand how the pituitary gland and hypothalamus can be involved in producing some symptoms of neurodegenerative diseases and inflammatory conditions one must first look at the hormones produced and secreted by the pituitary. The hormones of the pituitary are under the control of releasing factors and hormones produced and secreted from the hypothalamus by way of a special arterial capillary blood supply system. Technically, the connection between the hypothalamus and pituitary gland is called the hypothalamic-hypophyseal portal system.
The hormones released by the pituitary gland play an important role in many functions needed to maintain homeostasis (balance) in the body as mentioned above. For example, adrenocorticotrophic hormone plays an important role in maintaining blood pressure and blood sugar levels. Vasopressin, which is also known as antidiuretic hormone controls water volume in the body by way of the kidneys and arterioles. Follicle stimulating hormone controls sexual function and fertility. Growth hormone stimulates growth of tissues and bone. Luteinizing hormone controls sexual function and fertility in males and females. Oxytocin stimulates the uterus to contract during labor and the breasts to release milk. Prolactin stimulates female breast development and milk production. Thyroid stimulating hormone stimulates the release of hormones from the thyroid gland that regulate metabolism.
In hypopituitarism, there is a lack of one or more pituitary hormones. Lack of the hormone leads to loss of function in the gland or organ that it controls. As a result, problems with the pituitary gland can cause signs and symptoms such as the ceasing of menstrual periods, infertility, fatigue, and intolerance to stress and infection. In children, it can cause early onset of puberty, growth hormone deficiency, pituitary tumors, or pituitary gland dysfunction.
When they occur in children pituitary problems can cause visual disturbances, slowed growth and sexual development, as well as short stature such as under five feet. In adults, symptoms of empty sella syndrome and pituitary problems can develop slowly and vary greatly depending upon the hormones affected and
their target organs. Symptoms are abdominal pain, cessation of menstrual periods, decreased appetite, decreased sexual interest (especially in men), failure to release milk, fatigue, headache, infertility in women, lack of sex drive in women, loss of armpit or pubic hair, loss of body or facial hair in men, low
blood pressure, sensitivity to cold, visual disturbances, weakness and weight loss. Other symptoms can include facial swelling, hair loss, hoarseness or changing
voice, joint stiffness and weight gain.
Thyroid Stimulating Hormone
In the early stages, hypothyroidism due to pituitary malfunction can be associated with increased sensitivity to cold; constipation; weight gain; water retention; low heart rate; fatigue; decreased sweating; muscle cramps and joint pain; dry, itchy skin; thin, brittle fingernails; rapid thoughts; depression; poor muscle tone; female infertility and problems with menstrual cycles; and elevated blood cholesterol levels.
Late signs and symptoms of hypothyroidism include goiter, slow speech and a hoarse, breaking voice, deepening of the voice can also be noticed, dry puffy skin, especially on the face, thinning of the outer third of the eyebrows, abnormal menstrual cycles, low basal body temperature and depression.
Less common signs and symptoms of hypothyroidism include: impaired memory, impaired cognitive function, which is sometimes referred to as brain or cog fog by patients, inattentiveness, slow heart rate, diminished cardiac output and decreased contractility, reactive or post-prandial hypoglycemia, sluggish reflexes, hair loss, anemia, impaired intestinal iron and folate absorption or B12 deficiency from pernicious anemia, difficulty swallowing, shortness of breath with a shallow and slow respiratory pattern, increased need for sleep, irritability and mood instability.
The adrenal cortex produces corticosteroids which are a class of chemicals that includes steroid hormones. Corticosteroids are involved in a wide range of physiologic functions, including stress response, immune response, and regulation of inflammation, carbohydrate metabolism, protein catabolism (breakdown), blood electrolyte levels, and behavior. Glucocorticoids such as cortisol control carbohydrate, fat and protein metabolism and are anti-inflammatory by preventing phospholipid release, decreasing eosinophil action and a number of other mechanisms. Mineralocorticoids such as aldosterone control electrolyte and water levels, mainly by promoting sodium retention in the kidney.
Cortisol (hydrocortisone) is a glucocorticoid produced by the adrenal gland. It is released in response to stress and low levels of glucocorticoids in the blood. Its primary functions are to increase blood sugar by breaking down sugars stored as triglycerides and glycogen, a process known as gluconeogenesis; and suppress the immune system. Cortisol also assists in the metabolism of proteins, carbohydrates and fats. On the other hand, it decreases bone formation.
Beta Endorphin Hormone
Beta endorphins released by the pituitary gland are used as analgesics to numb or dull pain in the body. The pain dulls because endorphins binds to opioid receptors and activates them. Beta endorphins are about eighty times more powerful at decreasing pain than morphine. Beta endorphins are also believed to be helpful in slowing the growth of cancer cells. They are further associated with promoting a feeling of well-being and increased relaxation.
Empty Sella Syndrome
Empty sella syndrome (ESS) is a condtion in which cerebrospinal fluid is found inside the sella turcica. It is often discovered during tests to check for pituitary disorders. On brain scans the sella turcica appears to be empty and filled with CSF. In the T2 MRI image below, CSF appears white. The sella turcica also appears white instead of the gray shades, similar to the rest of the brain, due to CSF infiltration.
In children empty sella syndrome is associated with unusual facial features due to poor musculoskeletal development, increased bone density, headaches and problems with vision. In adults, it may be associated with no symptoms at all and only
rarely does it cause serious symptoms. About half of those adults that are affected have headaches. Some people have high blood pressure. In rare cases, CSF can leak through the ears and nose or cause problems with vision. In addition to brain scans, blood work is performed to check for increases or
decreases in hormones to check pituitary function. In most cases, hormone levels and blood test results are normal.
There are two types of empty sella syndrome. One is called primary and the other secondary empty sella syndrome. Primary empty sella syndrome is caused by a defect in the opening of the diaphrama sella. The pituitary stalk which connects the hypothalamus to the pituitary gland passes through the opening in the diaphrama sella. An increase in the size of the opening for the pituitary stalk causes CSF in the cisterns to enter the sella turcica compartment and compress the pituitary gland. Primary ESS is associated with obesity and high blood pressure in middle aged women. The condition is called idopathic intracranial hypertenison or benign intracranial hypertenison (BIH). I will discuss BIH further as this site grows and why I suspect that it affects overweight middle aged females far more frequently than males.
Secondary ESS is the result of the pituitary gland shrinking following an injury, surgery, or radiation therapy. It is called hypopituitarism (discussed above) and may be caused by brain surgery, brain tumor, head trauma, infections of the brain and meninges, radiation, stroke, subarachnoid hemorrhage (from a burst aneurysm), tumors of the pituitary gland or hypothalamus. It can also be caused by certain rare autoimmune-inflammatory disorders and metabolic disease. It is further interesting to note that it can also occur after pregnancy, which is a rare condition called Sheehan's syndrome. This is interesting because pregnancy poses similar challenges as female obesity to brain circulation.
Regardless of the cause, empty Sella Syndrome can cause the pituitary gland to malfunction. As mentioned above, it is attached by a stalk to the hypothalamus which produces releasing factors that regulate the pituitary gland. I suspect that the hypothalamus can also be affected by increased CSF volume in the ambient cistern of the brain and may play a role in dysautonomia and conditions such as multisystem atrophy.
The Suprasellar Cistern CSF and Pituitary Compression
Many of the signs and symptoms of pituitary malfunction are also found in neurodegenerative diseases. This could suggest similar causes. One possible cause is increased CSF volume or pressure in the suprasellar cistern.
The suprasellar cistern sits on top of the diaphrama sella. When viewed from above on an axial brain scan of a normal brain it has the shape of a five or six pointed star. As an aside, in addition to the pituitary stalk, the suprasellar cistern also contains the optic nerves (eye nerve), the opitic chiasma (crossover of eye nerves), and the circle of Willis (a circle of arteries at the base of the brain that connect the internal carotid and vertebral supply routes).
Interestingly, the eyes are frequently involved in many different conditions involving increased CSF volume or pressure in the brain due to their location which makes them vulnerabile to compression from many causes inside and outside the suprasellar cistern such as tumors, edema or hemorrhages. Compressive lesions are seen on brain scans as deformation of the normal star shape of the cistern. Whatever the cause, increased CSF volume, which is hydrocephalus or pressure in the suprasellar cistern can affect the pituitary stalk and gland, as well as the eyes. It can also affect the small arteries of the circle of Willis.
Physicians, scientists and researchers still debate about the exact clincal findings that indicate hydrocephalus. Most experts maintain that hydrocephalus should be associated with enlarged ventricles called ventriculomegaly. Others suggest, however, that an increase in CSF volume in the spaces outside the ventricles, called the extra axial spaces, such as the cisterns, should also be included as a form of hydrocephalus. Still other experts, such as Dr. David Harshfield Jr., a radiologist with expertise in upright MRI and hydrocephalus, look for even more subtle signs, such as enlarged perivascular spaces (Verchow-Robbins spaces), enlarged optic nerve sheaths and compression of Meckel's cave for example. This has led some experts to suggest that any disproportionate increase in CSF volume inside the cranial vault should be considered hydrocephalus.
In this regard, increased CSF volume and pressure in the brain causes compression of nerves and blood vessels. An increase in CSF volume and pressure in the ventricles can cause compression of the structures that surround them or press the surface of the brain against the cranial vault. The surface of the brain contains major blood vessels and compression due to increased CSF volume or pressure can decrease blood flow in and out of the brain.
In contrast to the ventricles, an increase in CSF volume in the cisterns can compress the structures of the brain they surround. Thus an increase in CSF volume or pressure in the suprasellar cistern can compress the pituitary stalk (infundibulum), which passes through it. In addition to its impact on the pituitary stalk, it also increases pressure on cover over the sella turcica called the diaphrama sella. A sudden or chronic increase in pressure on the diaphrama sellae can cause the opening for the pituitary stalk to enlarge and allow excess CSF volume from the suprasellar cistern to enter the sella turcica. An increase in CSF volume in the sella turcica can compress the pituitary. In any case, an increase in CSF volume, pressure or turbulance in the cisterns can cause the hypothalmaus and pituitary gland to malfunction.
One of the primary causes of increased CSF volume, pressure, backjets and turbulance in the cisterns of the brain is most likely due to upper cervical misalignments. The other likely cause is spondylosis (degeneration) of the spine.
For additional information see Cysts, Syrinxes and CSF.
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