by Dr. Gary Farr on 10 June 2002
Anatomy / Hormones
What is it?
The pituitary gland is a small oval endocrine gland that lies at the base of the brain. 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 anterior (front) lobe, or adenohypophysis, grows upward from the pharyngeal tissue at the roof of the mouth. The posterior (back) lobe, or neurohypophysis, grows downward from neural tissue. It is structurally continuous with the hypothalamus of the brain, to which it remains attached by the hypophyseal, or pituitary, stalk. 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
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.
Hormones produced by the pituitary gland
Anterior Pituitary
- Adrenocorticotrophic Hormone (ACTH)
- Thyroid-Stimulating Hormone (TSH)
- Luteinising Hormone (LH)
- Follicle-Stimulating Hormone (FSH)
- Prolactin (PRL)
- Growth Hormone (GH)
- Melanocyte-Stimulating Hormone (MSH)
Posterior Pituitary
- Anti-Diuretic Hormone (ADH)
- Oxytocin
The tissues in the anterior lobe secrete at least six different hormones. Growth hormone stimulates all the tissues in the body to grow by effecting protein formation.
The remaining five important hormones influence body functions by stimulating target organs. Adrenocorticotropic hormone (ACTH) controls the secretion of steroid hormones by the adrenal cortex, which affects glucose, protein, and fat metabolism; thyrotropin controls the rate of thyroxine synthesis by the thyroid gland, which is the principal regulator of body metabolic rate; prolactin, which regulates the formation of milk after the birth of an infant; and three separate gonadotropic hormones (follicle-stimulating hormone, luteinizing hormone, and luteotropic hormone) control the growth and reproductive activity of the gonads.
The release of each of the hormones from the anterior lobe is controlled by a specific substance secreted by nerve cells in the hypothalamus. These substances, called releasing factors, are transmitted by nerve fibers to tiny capillaries in the hypophyseal stalk. They move through blood vessels to the anterior lobe, where each releasing factor is responsible for the release of a specific pituitary hormone.
The two hormones that are produced by the posterior lobe, anti-diuretic hormone (ADH), and oxytocin, are synthesized by nerve cells in the hypothalamus. They are transported by nerve fibers to nerve endings in the posterior lobe, where they are released. Antidiuretic hormone (ADH or vasopressin), alters the permeability of the kidney tubules, permitting more water to be retained by the body. Oxytocin, which aids in the release of milk from mammary glands and causes uterine contractions. The only hormone that is synthesized by the intermediate lobe is the melanocyte-stimulating hormone, which appears to control skin pigmentation.
Table of pituitary hormones, targets and function
| 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.
Hormones produced by the hypothalamus
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:
- hormones that tell the pituitary to switch on production of a hormone (a releasing hormone); and
- hormones that tell the pituitary to switch off production of a hormone (an inhibiting hormone).
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.
Hormones produced by other glands in the body
In total more than 200 hormones or hormone-like substances have been discovered. In addition to the hormones listed in the table above, five of these hormones are controlled by hormones released by the pituitary.
Table of Hormones Under the Control of the Pituitary Gland
{fre_test_endo_hdr}
Disorders of the Pituitary Gland
Disorders of Pituitary Hormone Secretion
- Acromegaly
- Adult Growth Hormone Deficiency
- Craniopharyngioma
- Cushing's Disease
- Diabetes Insipidus
- Hypopituitarism
- Non-functioning tumors
- Prolactinoma
- Rarer Disorders, including Empty Sella Syndrome, Pituitary Infarction, Sheehan's Syndrome, Kallmann's Syndrome, Rathke's Cleft Cysts and Familial Multiple Endocrine Neoplasia Type 1, Wolfram Syndrome, & Septo-Optic Dysplasia
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.
Typical symptoms
- coarsening of facial features
- enlarged hands and feet
- thickening of the soft tissue in the palms and soles of the feet
- carpal tunnel syndrome (tingling feeling or pains in the hands)
- excessive sweating and oily skin
- headaches
- vision disturbances
- sleep apnea
- general tiredness
- irregular periods (oligomenorrhoea) or loss of normal menstrual function (amenorrhoea) - adult females
- impotence - adult males
- reduced fertility
- decrease in sex drive
All these symptoms tend to develop gradually and the changes may not be noticed for some time.
Adult Growth Hormone Deficiency (AGHD)
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.
Typical symptoms
- increase in adipose (fatty) tissue (especially around the waist)
- decrease in lean body mass (muscle)
- decrease in strength and stamina, reduction in exercise capacity
- decrease in bone density, increase in rate of fracture in middle age and beyond
- changes in blood cholesterol concentrations (increase in LDL and decrease in HDL)
- excessive tiredness
- anxiety and depression
- feelings of social isolation
- reduction in 'quality of life'
- increased sensitivity to cold or heat
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.
Typical symptoms
- headaches (sometimes accompanied by nausea or vomiting)
- diabetes insipidus
- disturbed sleep patterns
- vision disturbance
- behavioural changes, including introversion and inability to concentrate
- slow growth
- increased sensitivity to cold or heat
- early or delayed puberty - children
- irregular periods or loss of normal menstrual function
- (amenorrhoea) - adult females
- impotence - adult males
- reduced fertility - adults
- decrease in sex drive - adults
- tiredness and susceptibility to infections
- appetite and weight variations
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.
Typical symptoms
- behavioral changes, depression and mood swings, occasionally psychological problems can be severe
- face tends to be rounder (moon face) and redder
- weight gain around the trunk (central obesity)
- muscle wasting and proximal myopathy (patients have difficulty standing from a seated position without use of arms)
- tendency to bruise easily
- appearance of red 'stretch marks' on the abdomen, similar to those which occur during pregnancy
- irregular periods (oligomenorrhoea) or loss of normal menstrual function
- (amenorrhoea) - females
- impotence - males
- reduced fertility
- decrease in sex drive
- increase in hair growth on the face and body (hirsutism)
- increase in blood pressure
- development of mild diabetes mellitus
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.
Typical symptoms
- frequent need to pass urine (polyuria) even during the night
- extreme thirst leading to excessive drinking (polydipsia)
- imbalance of electrolytes (relatively high levels of sodium and potassium)
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.
Typical symptoms
- excessive tiredness and decreased energy
- muscle weakness
- reduced body hair
- irregular periods (oligomenorrhoea) or loss of normal menstrual function
- (amenorrhoea) - females
- impotence - males
- reduced fertility
- decrease in sex drive
- weight gain
- increased sensitivity to cold
- constipation
- dry skin
- pale appearance
- low blood pressure and dizziness on standing (postural hypotension)
- headaches
- vision disturbances
- diabetes insipidus
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.
Typical symptoms
- excessive tiredness and decreased energy
- muscle weakness
- reduced body hair
- irregular periods (oligomenorrhoea) or loss of normal menstrual function (amenorrhoea) - females
- impotence - males
- reduced fertility
- decrease in sex drive
- weight gain
- increased sensitivity to cold
- constipation
- dry skin
- pale appearance
- low blood pressure and dizziness on standing (postural hypotension)
- headaches
- vision disturbances
- diabetes insipidus
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.
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 (½ 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.
Typical Symptoms
- discharge from breasts (galactorrhoea) - females
- irregular periods (oligomenorrhoea) or loss of normal menstrual function
- (amenorrhoea) - adult females
- impotence - adult males
- reduced fertility
- decrease in sex drive
- headaches
- vision disturbance
- Empty Sella Syndrome
- Familial Multiple Endocrine Neoplasia Type 1 (FMEN1)
- Kallmann's Syndrome
- Pituitary Infarction
- Rathke's Cleft Cysts
- Septo-Optic Dysplasia (SOD)
- Sheehan's Syndrome
- Wolfram Syndrome (DIDMOAD)
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.
Prevention and Treatment of Pituitary Dysfunction
Contact Reflex Analysis Findings
The following reflexes are used to test the pituitary gland:
- {brain_sub_pineal} Pineal Gland Reflex
- {brain_sub_pituitary} Pituitary Brain Sub Reflex
- {brain_reflexes_sub_master_brain} Master Brain Reflex
These reflexes should be tested and treated with the proper supplementation.
{fre_test_endo_hdr}© Copyright 2000-2005, BecomeHealthyNow.com, Inc. All rights reserved.