The Pituitary Gland - Advanced Version

The pituitary gland is a small oval endocrine gland that lies at the base of the brain, nestled in a bony structure called the sella turcica. It is sometimes called the master gland of the body because all the other endocrine glands depend on its secretions for stimulation.

Functionally speaking, the pituitary is divided into two distinct lobes that arise from different embryological sources:

The hypothalamus controls almost all secretions of the pituitary. The posterior lobe is controlled by nerve fibers that originate in hypothalamic neurons and the anterior lobe by substances that are transported from the hypothalamus by tiny blood vessels (see image below).

Hormones are chemicals which circulate in the blood stream and spread around the body to carry messages or signals to different parts of the body. The name hormone comes from the Greek word hormao meaning "I excite" and refers to the fact that each hormone excites or stimulates a particular part of the body known as the target gland.

Hormones are made in endocrine glands and passed from the cells of the gland directly into the blood flowing through the gland. Generally, the higher the amount of hormone that is in the blood, the greater the effect its the targets.

Hormone	Target(s)	Function
ACTH	Adrenals	Stimulates the {adrenals} adrenal gland to produce a hormone called cortisol. ACTH is also known as corticotrophin.
TSH	Thyroid	Stimulates the {thyroid} thyroid gland to secrete its own hormone, which is called thyroxine. TSH is also known as thyrotrophin.
LH & FSH	Ovaries (Women) Testes (Men)	Controls reproductive functioning and sexual characteristics. Stimulates the {ovaries} ovaries to produce estrogen and progesterone and the testes to produce testosterone and sperm. LH and FSH are known collectively as Gonadotrophins. LH is also referred to as Interstitial cell stimulating hormone (ICSH) in males.
PRL	Breasts	Stimulates the {breasts} breasts to produce milk. This hormone is secreted in large amounts during pregnancy and breastfeeding, but is present at all times in both men and women.
GH	All cells in the body	Stimulates growth and repair. Research is currently being carried out to identify the functions of GH in adult life.
MSH		Exact role in humans unknown, but increases skin pigmentation in amphibians.
ADH	Kidneys	Controls the blood fluid and mineral levels in the body by affecting water retention by the {kidney} kidneys. This hormone is also known as vasopressin or arginine vasopressin (AVP).
Oxytocin	{repro_system_female} Uterus {breasts} breasts	Affects uterine contractions in pregnancy and birth and subsequent release of breast milk.

Control of hormone production is monitored continuously and regulated using feedback loops.

Hormone	Organ	Function
Cortisol	Adrenals	Cortisol has a number of functions. It promotes normal metabolism; maintains blood sugar levels and blood pressure; provides resistance to stress and acts as an anti-inflammatory agent. It also plays a part in regulation of fluid balance in the body.
Thyroxine	Thyroid	Thyroxine controls many body functions, including heart rate, temperature and metabolism. It also plays a role in the metabolism of calcium in the body.
Estrogen	Ovaries	Estrogen facilitates growth of the tissues of the sex organs and other tissues related to reproduction. Estrogen also acts to strengthen bones and has a protective effect on the heart.
Progesterone	Ovaries	Progesterone promotes the changes in the uterus that occur in preparation for the implantation of a fertilized ovum and prepares the breasts for milk production.
Testosterone	Testes	Testosterone is responsible for the characteristics of the masculine body, including hair growth on the face and body and muscle development. Testosterone is essential for the production or sperm and also acts to strengthen bones.

The secretion of hormones from the anterior pituitary is controlled by the production of hormones by the hypothalamus. Although there are a number of different hormones they can be split into two main types:

Thyrotropin is also called thyroid-stimulating hormone (TSH). Thyrotropin-producing cells (thyrotrophs) make up about 10 percent of the anterior pituitary and are located mainly in the center of the gland. Thyrotropin becomes attached firmly to receptors on the surface of the thyroid cells, forming thyroid follicles in the {thyroid} thyroid gland. Following binding, a complex train of events occurs so that preformed thyroid hormones are secreted and steps are set in motion for the synthesis of additional thyroid hormones. Thyrotropin exerts other pervasive effects. It stimulates the growth of thyroid cells and leads to increased blood flow through the gland. It also enhances the breakdown of thyroglobulin, a large thyroid-hormone-containing glycoprotein that is stored within the follicles of the thyroid gland.

The levels of thyrotropin in circulating fluids become elevated during thyroid hormone deficiency because there is no negative feedback inhibition of pituitary thyrotropin release by thyroid hormone. Elevated thyrotropin levels are found in other pathological states, including the presence of a thyrotropin-producing pituitary tumor. Low serum thyrotropin levels occur following damage to cells in the hypothalamus that produce thyrotropin-releasing hormone (TRH), following damage to the pituitary stalk, or, finally, following damage to the thyrotrophs themselves. Tests of increased sensitivity have made the measurement of thyrotropin in blood valuable in detecting subtle changes of both thyroid hyperfunction and hypofunction.

Gonadotrophs, which amount to about 7 percent of all pituitary cells, secrete two hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), but not in equal amount. The rate of secretion varies widely at different ages and at different times in the menstrual cycle of the female. Secretion of LH and FSH is low before puberty in both sexes. After puberty, about five times more LH than FSH is secreted. During menstrual cycles there is a dramatic rise in both hormones at the time of ovulation (see {ovaries} the ovary), and secretion increases as much as 15-fold following {menopause} menopause.

In men FSH stimulates the development of {repro_system_male} spermatozoa, in large part by acting on special cells in the testes called Sertoli cells. In women FSH stimulates the synthesis of estrogens as well as the maturation of cells lining the spherical, egg-containing structures known as the Graafian follicles. In menstruating women, there is a preovulatory surge in FSH levels in the blood. Inhibin, a hormone secreted by the Graafian follicles of the ovary and the Sertoli cells of the testis, inhibits the secretion of FSH from the pituitary gonadotroph.

In men androgens (male hormones) are secreted by specialized cells called Leydig cells, a process stimulated by LH. In women a preovulatory surge of LH is essential for rupture of the Graafian follicle so that the egg can be discharged on its journey to the uterus. The empty follicle becomes filled with other, progesterone-producing cells, transforming it into a corpus luteum.

When a disease process leads to encroachment on the cells of the pituitary gland, usually the first evidence of cell failure is in the gonadotroph. Thus, disappearance of menstrual periods may be the first sign of a pituitary tumor in the female. In the male the most common symptom of gonadotropin deficiency is impotence. Isolated deficiencies of both LH and FSH do occur, but only rarely. In a male, LH deficiency alone leads to the appearance of what has been described as a �fertile eunuch�; there is sufficient FSH present to permit the maturation of spermatozoa, but because of the LH deficiency the man has, nonetheless, many of the characteristics of a castrate. Tumors also can produce an excess of LH or FSH, and pituitary tumors that secrete only the nonspecific, hormonally inactive alpha unit of glycoprotein hormones are not rare.

Corticotropin, also called adrenocorticotropin hormone (ACTH), is a segment of a much larger prohormone glycoprotein molecule called pro-opiomelanocortin, which is synthesized by pituitary corticotrophs. This prohormone is split into a number of biologically active polypeptide fragments when the secretory granule is discharged from the cell. Among these hormones are corticotropin, whose major action is to stimulate growth and secretion of the cells of the adrenal cortex; alpha- and beta-melanotropin (melanocyte-stimulating hormone, MSH), which increases pigmentation of the skin; beta-lipotropin (LPH), which stimulates the release of fatty acids from adipose tissue; a small fragment of ACTH thought to improve memory; and beta-endorphin, a polypeptide that has excited a good deal of popular as well as scientific interest (see {adrenals} the adrenal cortex).

Beta-endorphins (along with the enkephalins, which are neuromodulators) were discovered when investigators postulated that, since opiates such as morphine bind firmly to cell-surface receptors, there must exist natural substances that do likewise and have a narcotic action. The endorphins and enkephalins are known, therefore, as endogenous (self-generated) opiates or opioids. They have powerful painkilling properties. Beta-endorphins instilled in the spinal fluid are capable of alleviating otherwise intractable pain in cancer patients. It has often been observed that severely traumatized individuals, those in battle, for example, appear to be free of pain. This phenomenon is due to the simultaneous release of beta-endorphin along with corticotropin in response to the stressful stimulus of the injury. There have also been reports of children with endorphin-producing pituitary tumors who are highly insensitive to pain. In addition, the release of endorphin or enkephalin may account for the euphoria (�high�) experienced by long-distance runners. Finally, there is evidence, not fully accepted, that endogenous opioids stimulate appetite. This is seen in rats and obese persons who have a rare disease called Prader-Labhart-Willi syndrome. In these instances, the appetite is diminished after the administration of a narcotic antagonist, such as naloxone.

Hyperplasia or adenoma of corticotrophs gives rise to the constellation of symptoms called Cushing's syndrome (discussed in more detail on the next page). A deficiency of corticotropin also occurs both as part of the multiple deficiencies of panhypopituitarism and as an isolated defect. The diagnosis of corticotropin deficiency is important because afflicted persons who are also subjected to stress can succumb to severe shock. Once frequently administered in the treatment of disorders including allergic states, collagen disorders, and autoimmune diseases, corticotropin has been largely displaced by a number of synthetic variants of adrenal steroids.

Melanocyte-stimulating hormone gets its name because of its effect on melanocytes: skin cells that contain the black pigment, melanin. In humans, melanocytes are responsible for moles, freckles, and suntan (and, if they turn cancerous, melanoma).

In most vertebrates, MSH is produced by an intermediate lobe of the pituitary gland. Its secretion causes a dramatic darkening of the skin of fishes, amphibians, and reptiles. The darkening occurs as granules of melanin spread through the branches of specialized melanocytes called melanophores.

Prolactin is a hormone produced by the anterior pituitary gland in both men and women. It is known as a gonadotrophic hormone as it affects the gonads (testes and ovaries). It also has an effect on other organs in the body, however, only the effects on the reproductive organs will be discussed here.

In males, prolactin influences the production of testosterone and affects sperm production. In conditions where prolactin secretion is increased (hyperprolactinaemia), testosterone levels drop and sperm production is reduced or absent, resulting in male infertility.

On the evolutionary scale, prolactin is an ancient hormone serving multiple roles in mediating the care of progeny (it has been called the �parenting� hormone). Prolactin is a large protein molecule synthesized and secreted from cells, the lactotrophs, which compose 20 percent of the anterior pituitary gland and are located largely in the two lateral portions. Unlike other anterior pituitary cells whose activities are stimulated by hypothalamic-releasing hormones, the major modulating influence on lactotroph secretion is the inhibitory effect of the neurotransmitter dopamine, which, in the case of prolactin, functions as a hypothalamic neurohormone.

The main action of prolactin in females is the induction and maintenance of lactation (breastfeeding). Prolactin levels build up during pregnancy but milk secretion does not begin until after birth. As an infant suckles, prolactin is released into the mother's blood stream, causing the milk glands to produce more milk. Prolactin and other hormones are responsible for the development of mammary glands during pregnancy. Prolactin also affects the ovaries. The main target area is the corpus luteum, the secretory organ formed from the ruptured ovarian follicle after ovulation. High prolactin levels lead to reduced progesterone function. The result of hyperprolactinaemia can be the non-appearance of menarche (beginning of menstruation at puberty), amenorrhoea (absence of menstruation in a woman after puberty) and anovulatory menstrual cycles (absence of ovulation i.e. no mature eggs produced). These effects can be the basis of female infertility.

Somatotrophs are plentiful in the pituitary, constituting 40 percent of the gland. They are located predominantly in the lateral lobes and secrete between one and two milligrams of growth hormone (GH; also called somatotropin) per day. Growth hormone stimulates growth, not only of bone but of essentially all the tissues of the body. In biochemical terms, growth hormone simultaneously stimulates protein synthesis in tissues and enhances the breakdown of fat to provide the energy for the stimulated growth. Growth hormone is also an insulin antagonist and, in susceptible individuals, can lead to elevated sugar levels in the blood and diabetes mellitus.

While GH may act on tissues directly, much of its effect is mediated by way of stimulating the liver and other tissues to manufacture and release secondary hormones, called somatomedins, which partly mimic the action of insulin. During childhood, somatomedin levels in the serum rise progressively with age, with an accelerated increase occurring at the time of the growth spurt of puberty, followed by a reduction to adult levels.

Growth hormone secretion is stimulated by growth hormone-releasing hormone (GHRH; also known as somatocrinin) and is inhibited by somatostatin. There are prominent daily fluctuations in growth hormone secretion in normal individuals, with the largest increase occurring shortly after the onset of sleep. Again, this increase is most pronounced at the time of puberty. Growth hormone levels in the serum are elevated in individuals with tumors that produce growth hormone, and its levels are unresponsive to stimulation in states of malnutrition.

The term acromegaly refers to the enlargement of the distal parts of the body; there is, in fact, progressive enlargement of the hands, feet, chin, and nose. Most other organs also become enlarged. The presence of a pituitary tumor causes severe headaches, and the pressure of the tumor on the optic chiasm causes visual defects.

The acromegalic patient has overgrown supraorbital ridges, enlarged nasal sinuses that give a sonorous quality to the voice, an overgrown jaw, spaces between the teeth, and an enlarged tongue. The skin thickens, producing a permanently furrowed brow. The enlarged fingers are no longer tapered and become spatulated.

Because the metabolic actions of growth hormone are antagonistic to those of insulin, some acromegalic patients develop diabetes mellitus and are subject to all of its complications. Other problems include elevated blood pressure, heart disease, and progressive arthritis. Finally, because some of these tumors produce prolactin as well as growth hormone, males may have enlarged breasts, and both sexes may show abnormal lactation (milk secretion). Acromegaly can be treated with a considerable degree of success with surgery, with X-ray therapy, and with drugs such as bromocriptine or a synthetic, long-acting somatostatin.

The posterior pituitary lobe consists largely of extensions of processes (axons) from large clusters of cell bodies called nuclei. One pair, known as the superoptic nuclei, lies immediately above the optic tract, while the other pair, the paraventricular nuclei, lies on each side of the third ventricle of the brain. This anatomical complex forms the neurohypophyseal unit. There are neural connections upward to other centers of the brain, including a centre that modulates thirst. The two major neurohypophyseal hormones, vasopressin (also called antidiuretic hormone [ADH]) and oxytocin, synthesized in the cell body of the nuclei, descend through the long axons to be stored in secretory granules in the posterior lobe of the pituitary. Functionally, therefore, the posterior lobe is a storage and secretion site only.

The hormones secreted by the posterior pituitary are produced in the hypothalamus and then passed down a tube between the hypothalamus and the pituitary (the pituitary stalk) when they are then secreted into the blood.

Oxytocin is responsible for uterine contractions, both before and after delivery. The muscle layers of the uterus (myometrium) become more sensitive to oxytocin near term. Towards the end of a term pregnancy, levels of progesterone decline, and contractions that were previously suppressed by progesterone begin to be more frequent and stronger. This change in the oxytocin/progesterone ratio is believed to be one of the initiators of labor.

Oxytocin is responsible for the contractions that bring about delivery, by thinning and dilating the cervix, and applying pressure that helps the baby descend in the pelvis. It is also important after delivery, as it continues to cause the myometrium to contract. These contractions help constrict the blood vessels that are sending blood to the uterus at the time of childbirth at the rate of a liter a minute!

Oxytocin is also responsible for milk ejection during breastfeeding, by contraction of the myoepithelial cells in the lactating mammary gland. The uterine "cramping" that often occurs with breastfeeding is a signal that oxytocin is still causing the uterus to contract after delivery. These contractions help the uterine muscle to continue to constrict the uterine blood vessels, and bring about a decrease in the amount of vaginal bleeding after delivery.

The function of ADH is to inhibit or prevent the formation of urine. Osmoreceptors monitor the solute concentrations in the blood. During pregnancy the osmoreceptors are "reset" to deal with the increased blood volume of pregnancy. If the osmoreceptors send excitatory messages to the "ADH secreting neurones," less urine is produced, leaving more volume in the circulating blood.

The actions of the hormones of the posterior pituitary are especially important to consider in the pregnant woman who is at risk for preterm labor. Maternal dehydration may trigger the secretion of ADH by the posterior pituitary. It is thought that oxytocin may also be released at the same time, bringing about uterine contraction before the optimum time. These uterine contractions, or uterine "irritability" (low intensity, high frequency contractions) of preterm labor are often treated with maternal hydration. Women at risk for preterm labor are encouraged to drink copious amounts of water throughout the day. And, if hospitalized for contractions, hydration with a bolus of IV fluid is often effective to "quiet" the uterus.

Secretion of ADH is also stimulated by pain, low blood pressure and drugs such as nicotine, morphine and barbiturates. In trauma situations, a great deal of ADH is released, to counteract blood loss. The result is constriction of smooth muscles of the blood vessels, in order to raise the arterial blood pressure. (As a result, of this "pressor" effect, ADH is sometimes referred to as vasopressin.) Very little blood is getting to the baby through the constricted blood vessels.

Acromegaly is caused when a tumor on the pituitary gland produces too much growth hormone (GH). These tumors are almost always benign (i.e. not cancerous) and therefore do not spread to other areas of the body.

Acromegaly is a very rare condition and usually develops between the ages of 30 and 50. If the condition develops before a person has stopped growing (which usually occurs between the ages of 15 to 17 years of age), it causes gigantism because growth hormone promotes growth of bones in the body.

All these symptoms tend to develop gradually and the changes may not be noticed for some time.

Growth Hormone (GH) is a protein made in the pituitary gland and passed from there into the blood stream. GH has effects on virtually all the organs of the body, but its primary use during childhood is making children grow.

GH deficiency is usually caused by damage to the pituitary gland or the part of the brain which controls this gland (the hypothalamus). The damage may be due to a tumor or to the effects of treatment for the tumor (surgery or radiotherapy) or to problems with the blood supply to the pituitary gland.

There are many causes of short stature or dwarfism other than deficient growth hormone secretion; for example, chromosomal abnormalities, malnutrition (including poorly controlled diabetes mellitus), thyroid deficiency, and disorders of bone formation are all examples of dwarfism with normal GH secretion. Nonetheless, growth hormone deficiency is a fairly common cause of short stature. Perhaps most frequent is GH deficiency resulting from damage to the hypothalamus and pituitary during fetal development or at birth because of trauma, lack of oxygen, or any of a number of other causes. When damage to the hypothalamus or pituitary is mild, growth hormone deficiency may be the only detectable manifestation of a disease state because the somatotrophs are the most sensitive of the pituitary cells to injury. When all of the cells of the pituitary are severely damaged or destroyed the patient is said to have panhypopituitarism (leading to diminished function of the gonads, the thyroid, and the adrenal glands).

Midgets usually suffer from one of two forms of hereditary (familial) isolated growth hormone deficiency. In some families the deficiency is the result of underproduction of GHRH, in which case growth hormone secretion may be stimulated by infusion of GHRH. In others, the problem lies in the somatotrophs themselves when they become incapable of manufacturing growth hormone. Growth hormone levels also tend to fall in some aged persons who otherwise appear to be normal.

In other forms of dwarfism, the hypothalamus and pituitary function adequately, and the abnormality lies rather in the lack of response of body tissues. A well-studied example is that of the Laron dwarf. These children suffer from a hereditary disorder characterized by the inability of growth hormone to bind to specific receptors in the body's tissues; circulating GH levels are elevated but somatomedin levels remain low because GH, unable to bind to receptors, cannot stimulate somatomedin secretion. Another example is the African Pygmy, in whom there is a resistance to the administration of GH. This is caused by an unresponsiveness to somatomedin, which suggests that there is a defect in the somatomedin receptors.

Growth hormone alone cannot generate growth without an adequate supply of food, so that in states of malnutrition dwarfism occurs in the face of a mild elevation in growth hormone concentrations in the blood.

Finally, an example of the effect of emotional and environmental factors on growth is found in the condition known as psychosocial dwarfism. Such children suffer emotional deprivation from uncaring or abusive parents. Growth hormone levels are low but return to normal along with an increased rate of growth when the children are removed to a more supportive environment, only to have the cycle repeated when the child is returned to the custody of the parents. These victims tend to be withdrawn and apathetic. They have disrupted sleep and bizarre eating and drinking habits. All of these symptoms are dramatically reversed when the child is removed to compassionate care in a hospital or foster home.

An adult GH-deficient dwarf has the body proportions of a young child. Radiographs (X-ray pictures) of growing ends of bone also show growth retardation in relation to the patient's chronological age. These changes are not apparent at birth but appear some time within the first two years of life. Puberty is often delayed, but untreated individuals may be fertile and give birth to normal children. When it appears in adults, GH deficiency produces only subtle changes, with minor decreases in strength and in the density of bones.

Growth hormone-deficient dwarfs respond dramatically to injections of human growth hormone. Supplies of GH were greatly limited in the past because the only source was GH extracted from human pituitary glands obtained at autopsies. With the availability of human GH manufactured by recombinant DNA technology using bacteria, the supply is potentially unlimited. Most treated patients achieve normal height, but in some, particularly those with the hereditary inability to synthesize growth hormone, antibodies to the injected growth hormone may block the therapeutic action. There is evidence that children with �constitutional short stature,� that is, children from otherwise normal families in whom short stature is the rule in the absence of disease, may also respond to GH treatment.

Excess levels of growth hormone are most often caused by a benign tumor (adenoma) of somatotrophs of the pituitary gland. Rarely, a tumor of the lung or the pancreatic islets produces GHRH, which stimulates normal pituitary somatotrophs to excess secretion when released into the circulation. Even more rarely is there excessive, ectopic production of GH by tumor cells that do not ordinarily synthesize GH. If hypersecretion of growth hormone occurs during childhood, growth progresses at an inordinately rapid rate to extremes, 8 feet, 11 inches in the case of the �Alton Giant.� Giantism is rare because such individuals usually have all of the infirmities described below for acromegaly.

Craniopharyngiomas are very rare benign (non-cancerous) tumors, with 50% occurring in children under 16 years, and the remainder at any time in adult life.

The tumors can be solid, cystic (full of fluid), calcified, or full of debris. They are slow-growing tumors that can take 2-3 years (or longer) to manifest themselves before a diagnosis is made.

Cushing's syndrome describes the condition resulting from too much exposure to steroid hormones.

The commonest cause of Cushing's syndrome (apart from the use of synthetic steroids to treat other conditions) is Cushing's disease. This is a problem arising in the pituitary gland caused by a tumor which overproduces a hormone called ACTH. This in turn stimulates the adrenal glands to overproduce the steroid hormone cortisol. Cushing's syndrome can also be caused by a small growth in one, or both, of the adrenal glands.

Cushing's is rare and is more often found in women than in men. It can affect all age groups, but the peak incidence is in middle age.

Because Cushing's progresses slowly and gradually in most cases, it can go unrecognized for some time.

Diabetes Insipidus (DI) is a disorder in which the kidneys are unable to retain water. This results in the production of large amounts of urine which in turn makes you feel dry and very thirsty.

Neurogenic Diabetes Insipidus
This condition is caused by the lack of a water-retaining hormone or chemical in the blood (called vasopressin or ADH). Neurogenic DI is sometimes referred to as Cranial, Central or Pituitary DI.

Nephrogenic Diabetes Insipidus
This condition is caused by an abnormality in the kidneys which prevents the kidneys from responding to the water-retaining hormone.

Diabetes insipidus is not related to the type of diabetes most people have heard of, diabetes mellitus.

The pituitary gland produces a number of hormones or chemicals which are released into the blood to control other glands in the body. If the pituitary is not producing one or more of these hormones, or not producing enough, then this condition is known as hypopituitarism. The term Multiple Pituitary Hormone Deficiency (MPHD) is sometimes used to describe the condition when the pituitary is not producing two or more of these hormones. If all the hormones produced by the pituitary are affected this condition is known as panhypopituitarism.

Hypopituitarism is most often caused by a benign (i.e. not cancerous) tumor of the pituitary gland, or of the brain in the region of the hypothalamus. Pituitary underactivity may be caused by the direct pressure of the tumor mass on the normal pituitary or by the effects of surgery or radiotherapy used to treat the tumor. Less frequently, hypopituitarism can be caused by infections (such as meningitus) in or around the brain or by severe blood loss, by head injury, or by various rare diseases such as sarcoidosis (an illness which resembles tuberculosis).

More information about conditions which result in hypopituitarism can be found in the Rarer Disorders section.

Each of the symptoms described above occur in response to the loss of one or more of the hormones produced by the pituitary. Decrease in the production of only one hormone would not lead to all the symptoms described above.

By far the most common type of tumor of the pituitary gland (about half of all cases) is the 'non-functioning' tumor. This is a tumor which does not produce any hormones itself. It can cause headaches and visual problems or it can press on the pituitary gland, causing it to stop producing the required amount of one or more of the pituitary hormones, leading to hypopituitarism.

A prolactinoma is a prolactin-producing tumor of the pituitary gland. These tumors come in various sizes, but the vast majority are less than 10mm (� inch) in diameter. These are called microprolactinomas. The rarer large tumors are called macroprolactinomas. Prolactinomas can occur in both men and women.

Very few patients with prolactinomas require surgery, as most prolactinomas (particularly microprolactinomas) shrink in size following treatment with medication.

Empty Sella Syndrome
This condition occurs when pituitary tissue is destroyed without undergoing pituitary surgery or radiotherapy, but there is no evidence of a pituitary tumour. The initial cause of empty sella syndrome may not be clear and may have occurred much earlier.

Familial Multiple Endocrine Neoplasia Type 1 (FMEN1)
Familial multiple endocrine neoplasia type 1 is an inherited disorder affecting the endocrine glands. The disorder affects both males and females equally. FMEN1 is also sometimes called Wermer Syndrome.

People with FMEN1 carry a gene which makes them prone to the development of pituitary tumors, parathyroid disease, tumors in the pancreas and occasionally tumors in the other endocrine glands. The parathyroids are the glands most often affected by FMEN1 and the pituitary becomes overactive in about 1 in 6 persons. The cause of pitutary overactivity is usually a benign tumour called a prolactinoma.

Kallmann's Syndrome
Kallmann's syndrome is a form of hypogonadotrophic hypogonadism characterised by an absence of GnRH, a hormone naturally released by the hypothalamus. Sufferers fail to go through puberty unless they are given sex hormone replacement therapy and in addition usually have no sense of smell (anosmia).

Pituitary Infarction
If the blood supply to the pituitary is restricted, the gland tissue can die resulting in hypopituitarism. Infarctions can occur as a result of impaired blood flow to the pituitary gland or head trauma.

Rathke's Cleft Cysts
Rathke's cleft cysts are not tumors, but instead are classified as developmental abnormalities. Like craniopharyngiomas, these cysts form during early development of the foetus from a structure known as Rathke's pouch. Small Rathke's cleft cysts are not uncommon and do not usually cause any symptoms. Problems can occur if these cysts enlarge and interfere with pituitary production or exert pressure on the optic chiasm.

Septo-Optic Dysplasia (SOD)
Septo-optic dysplasia is a rare condition affecting both children and adults which consists of three main abnormalities. These are as follows:

Abnormal eye development
Occasionally one or both eyes may be abnormal or the nerves connecting the eyes to the brain may be abnormal.

Abnormal development of the front part of the brain (forebrain)
Structures called the septum pellucidum and the corpus callosum which divide the forebrain into two may be absent.

Abnormal pituitary gland development
The pituitary gland produces a number of chemicals called hormones controlling growth and development in children. Additionally, the posterior part of the pituitary produces a hormone called vasopressin which makes sure that fluid is retained in the body and patients do not become dehydrated. The pituitary gland is very much a master gland which controls other glands in the body such as the adrenal and thyroid gland.

Adults and children with SOD may have any of these features. Most have two out of the three cardinal features. Approximately one third will have all three problems.

Sheehan's Syndrome
The pituitary gland doubles in size during normal pregnancy. Under these circumstances a sudden drop in blood pressure can result in pituitary infarction leading to pan-hypopituitarism.

Wolfram Syndrome
Consists of diabetes insipidus, diabetes mellitus, optic atrophy and deafness. Also known by the acronym DIDMOAD. It is usually a familial disorder.

The following reflexes are used to test the pituitary: It is important to note that it takes a skilled practitioner to find the root cause of the person's problem when dealing with endocrine problems.