Pituitary Gland: From 3 Different Sources
Sometimes referred to as the master gland, the pituitary is the most important endocrine gland. It regulates and controls the activities of other endocrine glands and many body processes. The pituitary gland is a pea-sized structure attached by a stalk of nerve fibres to the hypothalamus. The anterior lobe produces growth hormone; prolactin; ACTH; TSH (thyroid-stimulating hormone), which stimulates hormone production by the thyroid gland; the gonadotrophins FSH (follicle stimulating hormone) and LH (luteinizing hormone); and melanocyte-stimulating hormone (MSH), which controls darkening of the skin. The posterior pituitary secretes ADH and oxytocin.
Also known as the pituitary body and the hypophysis, this is an ovoid structure, weighing around 0·5 gram in the adult. It is attached to the base of the BRAIN, and lies in the depression in the base of the skull known as the sella turcica. The anterior part is called the adenohypophysis and the posterior part the neurohy-P pophysis. The gland is connected to the HYPOTHALAMUS of the brain by a stalk known as the hypophyseal or pituitary stalk.
The pituitary gland is the most important ductless, or endocrine, gland in the body. (See
ENDOCRINE GLANDS.) It exerts overall control of the endocrine system through the media of a series of hormones which it produces. The adenohypophysis produces trophic hormones (that is, they work by stimulating or inhibiting other endocrine glands) and have therefore been given names ending with ‘trophic’ or ‘trophin’. The thyrotrophic hormone, or thyroid-stimulating hormone (TSH), exerts a powerful in?uence over the activity of the THYROID GLAND. The ADRENOCORTICOTROPHIC HORMONE (ACTH) stimulates the cortex of the adrenal glands. GROWTH HORMONE, also known as somatotrophin (SMH), controls the growth of the body. There are also two gonadotrophic hormones which play a vital part in the control of the gonads: these are the follicle-stimulating hormone (FSH), and the luteinising hormone (LH) which is also known as the interstitial-cell-stimulating hormone (ICSH) – see GONADOTROPHINS. The lactogenic hormone, also known as prolactin, mammotrophin and luteotrophin, induces lactation.
The neurohypophysis produces two hormones. One is oxytocin, which is widely used because of its stimulating e?ect on contraction of the UTERUS. The other is VASOPRESSIN, or the antidiuretic hormone (ADH), which acts on the renal tubules and the collecting tubules (see KIDNEYS) to increase the amount of water that they normally absorb.
(hypophysis) the master endocrine gland: a pea-sized body attached beneath the *hypothalamus in a bony cavity at the base of the skull. It has an anterior lobe (adenohypophysis), which secretes *thyroid-stimulating hormone, *ACTH (adrenocorticotrophic hormone), the *gonadotrophins, *growth hormone, *prolactin, *lipotrophin, and *melanocyte-stimulating hormone. The secretion of all these hormones is regulated by specific releasing hormones, which are produced in the hypothalamus (see also corticotrophin-releasing hormone; gonadotrophin-releasing hormone; thyrotrophin-releasing hormone). The posterior lobe (neurohypophysis) secretes *vasopressin and *oxytocin, which are synthesized in the hypothalamus and transported to the pituitary, where they are stored before release.
See MONONUCLEOSIS.... glandular fever
A gland that secretes its products through a duct to the surface of the body or of an organ. The sweat glands in the skin and the salivary glands in the mouth are examples. The secretion is set o? by a hormone (see HORMONES) or a NEUROTRANSMITTER.... exocrine gland
See BREASTS.... mammary gland
This is an accessory sex gland in males which is wrapped round the URETHRA as this tube leaves the URINARY BLADDER. Opening into the urethra, the gland secretes an alkaline ?uid during ejaculation and is a constituent of SEMEN. The gland grows during adolescence and is sensitive to the concentrations of sex hormones.... prostate gland
The glands that produce the saliva injected when a mosquito or other ectoparasite bites, which prevent blood from clotting while the mosquito feeds.... salivary glands
See ADRENAL GLANDS.... suprarenal glands
Any one of certain glands in the body the secretion of which goes directly into the bloodstream and so is carried to di?erent parts of the body. These glands – the pituitary, thyroid, parathyroid, adrenal and reproductive – are also known as the ENDOCRINE GLANDS. Some glands may be both duct glands and ductless glands. For example, the PANCREAS manufactures a digestive juice which passes by a duct into the small intestine. It also manufactures, by means of special cells, a substance called INSULIN which passes straight into the blood.... ductless gland
Organs whose function it is to secrete into the blood or lymph, substances known as HORMONES. These play an important part in general changes to or the activities of other organs at a distance. Various diseases arise as the result of defects or excess in the internal secretions of the di?erent glands. The chief endocrine glands are:
Adrenal glands These two glands, also known as suprarenal glands, lie immediately above the kidneys. The central or medullary portion of the glands forms the secretions known as ADRENALINE (or epinephrine) and NORADRENALINE. Adrenaline acts upon structures innervated by sympathetic nerves. Brie?y, the blood vessels of the skin and of the abdominal viscera (except the intestines) are constricted, and at the same time the arteries of the muscles and the coronary arteries are dilated; systolic blood pressure rises; blood sugar increases; the metabolic rate rises; muscle fatigue is diminished. The super?cial or cortical part of the glands produces steroid-based substances such as aldosterone, cortisone, hydrocortisone, and deoxycortone acetate, for the maintenance of life. It is the absence of these substances, due to atrophy or destruction of the suprarenal cortex, that is responsible for the condition known as ADDISON’S DISEASE. (See CORTICOSTEROIDS.)
Ovaries and testicles The ovary (see OVARIES) secretes at least two hormones – known, respectively, as oestradiol (follicular hormone) and progesterone (corpus luteum hormone). Oestradiol develops (under the stimulus of the anterior pituitary lobe – see PITUITARY GLAND below, and under separate entry) each time an ovum in the ovary becomes mature, and causes extensive proliferation of the ENDOMETRIUM lining the UTERUS, a stage ending with shedding of the ovum about 14 days before the onset of MENSTRUATION. The corpus luteum, which then forms, secretes both progesterone and oestradiol. Progesterone brings about great activity of the glands in the endometrium. The uterus is now ready to receive the ovum if it is fertilised. If fertilisation does not occur, the corpus luteum degenerates, the hormones cease acting, and menstruation takes place.
The hormone secreted by the testicles (see TESTICLE) is known as TESTOSTERONE. It is responsible for the growth of the male secondary sex characteristics.
Pancreas This gland is situated in the upper part of the abdomen and, in addition to the digestive enzymes, it produces INSULIN within specialised cells (islets of Langerhans). This controls carbohydrate metabolism; faulty or absent insulin production causes DIABETES MELLITUS.
Parathyroid glands These are four minute glands lying at the side of, or behind, the thyroid (see below). They have a certain e?ect in controlling the absorption of calcium salts by the bones and other tissues. When their secretion is defective, TETANY occurs.
Pituitary gland This gland is attached to the base of the brain and rests in a hollow on the base of the skull. It is the most important of all endocrine glands and consists of two embryologically and functionally distinct lobes.
The function of the anterior lobe depends on the secretion by the HYPOTHALAMUS of certain ‘neuro-hormones’ which control the secretion of the pituitary trophic hormones. The hypothalamic centres involved in the control of speci?c pituitary hormones appear to be anatomically separate. Through the pituitary trophic hormones the activity of the thyroid, adrenal cortex and the sex glands is controlled. The anterior pituitary and the target glands are linked through a feedback control cycle. The liberation of trophic hormones is inhibited by a rising concentration of the circulating hormone of the target gland, and stimulated by a fall in its concentration. Six trophic (polypeptide) hormones are formed by the anterior pituitary. Growth hormone (GH) and prolactin are simple proteins formed in the acidophil cells. Follicle-stimulating hormone (FSH), luteinising hormone (LH) and thyroid-stimulating hormone (TSH) are glycoproteins formed in the basophil cells. Adrenocorticotrophic hormone (ACTH), although a polypeptide, is derived from basophil cells.
The posterior pituitary lobe, or neurohypophysis, is closely connected with the hypothalamus by the hypothalamic-hypophyseal tracts. It is concerned with the production or storage of OXYTOCIN and vasopressin (the antidiuretic hormone).
PITUITARY HORMONES Growth hormone, gonadotrophic hormone, adrenocorticotrophic hormone and thyrotrophic hormones can be assayed in blood or urine by radio-immunoassay techniques. Growth hormone extracted from human pituitary glands obtained at autopsy was available for clinical use until 1985, when it was withdrawn as it is believed to carry the virus responsible for CREUTZFELDT-JAKOB DISEASE (COD). However, growth hormone produced by DNA recombinant techniques is now available as somatropin. Synthetic growth hormone is used to treat de?ciency of the natural hormone in children and adults, TURNER’S SYNDROME and chronic renal insu?ciency in children.
Human pituitary gonadotrophins are readily obtained from post-menopausal urine. Commercial extracts from this source are available and are e?ective for treatment of infertility due to gonadotrophin insu?ciency.
The adrenocorticotrophic hormone is extracted from animal pituitary glands and has been available therapeutically for many years. It is used as a test of adrenal function, and, under certain circumstances, in conditions for which corticosteroid therapy is indicated (see CORTICOSTEROIDS). The pharmacologically active polypeptide of ACTH has been synthesised and is called tetracosactrin. Thyrotrophic hormone is also available but it has no therapeutic application.
HYPOTHALAMIC RELEASING HORMONES which affect the release of each of the six anterior pituitary hormones have been identi?ed. Their blood levels are only one-thousandth of those of the pituitary trophic hormones. The release of thyrotrophin, adrenocorticotrophin, growth hormone, follicle-stimulating hormone and luteinising hormone is stimulated, while release of prolactin is inhibited. The structure of the releasing hormones for TSH, FSH-LH, GH and, most recently, ACTH is known and they have all been synthesised. Thyrotrophin-releasing hormone (TRH) is used as a diagnostic test of thyroid function but it has no therapeutic application. FSH-LH-releasing hormone provides a useful diagnostic test of gonadotrophin reserve in patients with pituitary disease, and is now used in the treatment of infertility and AMENORRHOEA in patients with functional hypothalamic disturbance. As this is the most common variety of secondary amenorrhoea, the potential use is great. Most cases of congenital de?ciency of GH, FSH, LH and ACTH are due to defects in the hypothalamic production of releasing hormone and are not a primary pituitary defect, so that the therapeutic implication of this synthesised group of releasing hormones is considerable.
GALACTORRHOEA is frequently due to a microadenoma (see ADENOMA) of the pituitary. DOPAMINE is the prolactin-release inhibiting hormone. Its duration of action is short so its therapeutic value is limited. However, BROMOCRIPTINE is a dopamine agonist with a more prolonged action and is e?ective treatment for galactorrhoea.
Thyroid gland The functions of the thyroid gland are controlled by the pituitary gland (see above) and the hypothalamus, situated in the brain. The thyroid, situated in the front of the neck below the LARYNX, helps to regulate the body’s METABOLISM. It comprises two lobes each side of the TRACHEA joined by an isthmus. Two types of secretory cells in the gland – follicular cells (the majority) and parafollicular cells – secrete, respectively, the iodine-containing hormones THYROXINE (T4) and TRI-IODOTHYRONINE (T3), and the hormone CALCITONIN. T3 and T4 help control metabolism and calcitonin, in conjunction with parathyroid hormone (see above), regulates the body’s calcium balance. De?ciencies in thyroid function produce HYPOTHYROIDISM and, in children, retarded development. Excess thyroid activity causes thyrotoxicosis. (See THYROID GLAND, DISEASES OF.)... endocrine glands
Numerous glands within the tarsal plates of the eyelids. Their secretions form part of the tears. (See EYE.)... meibomian glands
One of the SALIVARY GLANDS. It is situated just in front of the ear, and its duct runs forwards across the cheek to open into the interior of the mouth on a little projection opposite the second last tooth of the upper row. The parotid gland is generally the ?rst of the salivary glands to become enlarged in MUMPS.... parotid gland
A small reddish structure, 10 mm in length and shaped somewhat like a pine cone (hence its name), situated on the upper part of the midbrain (see BRAIN). Many theories have been expounded as to its function, but there is increasing evidence that, in some animals at least, it is affected by light and plays a part in hibernation and in controlling sexual activity and the colour of the skin. This it seems to do by means of a substance it produces known as MELATONIN. There is also growing evidence that it may play a part in controlling the circadian rhythms of the body – the natural variations in physiological activities throughout the 24-hour day.... pineal gland
A collection of CELLS or an ORGAN with a specialised ability to make and secrete chemical substances such as enzymes and hormones essential for the normal functioning of the body. Glands are classi?ed into two groups: ENDOCRINE and EXOCRINE. The former secrete their products, hormones, straight into the bloodstream; the latter’s secretions are discharged through ducts. (These functional differences are the reason why glands have been de?ned as ductless and ducted.) Examples of endocrine glands are the adrenals, PITUITARY GLAND and THYROID GLAND. Exocrine glands include SEBACEOUS GLANDS (in the skin) and the SALIVARY GLANDS in the mouth whose enzymes start the digestion of food. The BREASTS or mammary glands are exocrine glands that secrete milk. Though strictly speaking not a gland, LYMPH nodes (part of the lymphatic system) are sometimes called that. While they do not produce secretions, lymph glands do release white blood cells, an essential part of the body’s defence system.... gland
Oil secreting glands, mostly clustered around hair follicles. The oil, sebum, is released into the oil glands from the disintegrated cytoplasm of shedding holocrine cells that line the alveolar surfaces. The nature of the secretion is a direct reflection of the state of the body’s lipid metabolism.... sebaceous gland
The minute glands situated alongside hairs and opening into the follicles of the latter a short distance below the point at which the hairs emerge on the surface. These glands secrete an oily material, and are especially large upon the nose, where their openings form pits that are easily visible. In the mouth the glands open directly on the mucosal surface. (See also SKIN.)... sebaceous glands
See SKIN.... sweat glands
A pair of oval, peasized glands whose ducts open into the vulva (the folds of flesh that surround the opening of the vagina). During sexual arousal, these glands secrete a fluid to lubricate the vulval region. Infection of the glands causes bartholinitis.... bartholin’s glands
A gland that secretes hormones directly into the bloodstream rather than through a duct. Examples include the thyroid gland, pituitary gland, ovaries, testes, and adrenal glands. (See also exocrine gland.)... endocrine gland
An infection of horses caused by the bacterium PSEUDOMONAS MALLEI. In rare cases, it is transmitted to humans, causing symptoms including fever and general aches and pains. Ulcers may develop where bacteria entered the skin; if bacteria enters the lungs, pneumonia may occur. In severe cases, septicaemia may follow. Treatment is with antibiotics.... glanders
... adenitis means inflammation of a gland.
Two small glands opening either side of the external vaginal ori?ce. Their secretions help to lubricate the vulva, when a woman is sexually aroused. The glands may become infected and very painful; sometimes an abscess develops and local surgery is required. Otherwise antibiotics, analgesics and warm baths are usually e?ective.... bartholin’s glands
Also known as the bulbourethral glands, these are a pair of glands whose ducts open into the urethra at the base of the PENIS. They secrete a ?uid that is one of the constituents of the SEMEN which carries the spermatozoa and is ejaculated into the VAGINA during coitus (sexual intercourse).... cowper’s glands
A unicellular gland in cestodes, which encircles the ootype. Its function is not known.... mehlis’s glands
compound glands of the small intestine, found in the *duodenum and the upper part of the jejunum. They are embedded in the submucosa and secrete mucus. [J. C. Brunner (1856–1927), Swiss anatomist]... brunner’s glands
small glands in the mucous membrane lining the mouth. They secrete material that mixes with saliva.... buccal glands
see Cowper’s glands.... bulbourethral glands
(bulbourethral glands) a pair of small glands that open into the urethra at the base of the penis. Their secretion contributes to the seminal fluid, but less than that of the prostate gland or seminal vesicles. [W. Cowper (1660–1709), English surgeon]... cowper’s glands
tubular glands that lie in the mucous membrane of the stomach wall. There are three varieties: the cardiac, parietal (oxyntic), and pyloric glands, and they secrete *gastric juice.... gastric glands
(crypts of Lieberkühn) simple tubular glands in the mucous membrane of the *intestine. In the small intestine they lie between the villi. They are lined with columnar *epithelium in which various types of secretory cells are found. In the large intestine Lieberkühn’s glands are longer and contain more mucus-secreting cells. [J. N. Lieberkühn (1711–56), German anatomist]... lieberkühn’s glands
acute intrapituitary haemorrhage, usually into an existing tumour, presenting as severe headache and collapse. It is a medical emergency. Due to the sudden expansion in size of the gland with the haemorrhage, it is accompanied by lesions of the cranial nerves running close to the pituitary gland, causing paralysis of the muscles of the orbit and occasionally the face. Anterior pituitary insufficiency usually results, but posterior pituitary function survives. Surprisingly, pituitary function usually recovers.... pituitary apoplexy
modified sebaceous glands on the inner surface of the *prepuce.... preputial glands
a gland that produces *saliva. There are three pairs of salivary glands: the *parotid glands, *sublingual glands, and *submandibular glands (see illustration). They are stimulated by reflex action, which can be initiated by the taste, smell, sight, or thought of food.... salivary gland
one of a pair of *salivary glands situated in the lower part of the mouth, one on either side of the tongue. The sublingual glands are the smallest salivary glands; each gland has about 20 ducts, most of which open into the mouth directly above the gland.... sublingual gland
An endocrine gland somewhat behind the eyes and suspended from the front of the brain. The front section, the anterior pituitary, makes and secretes a number of controlling hormones that affect the rate of oxidation; the preference for fats, sugars, or proteins for fuel; the rate of growth and repair in the bones, connective tissue, muscles, and skin; the ebb and flow of steroid hormones from both the gonads and adrenal cortices. It does this through both negative and positive feedback. The hypothalamus controls these functions, secreting its own hormones into a little portal system that feeds into the pituitary, telling the latter what and how much to do. The hypothalamus itself synthesizes the nerve hormones that are stored in the posterior pituitary, which is responsible for squirting them into the blood when the brain directs it to. These neurohormones act quickly, like adrenalin, to constrict blood vessels, limit diuresis in the kidneys, and trigger the complex responses of sexual excitation, milk letdown in nursing, and muscle stimulus in the uterus (birthing, orgasm, and menstrual contractions), prostate, and nipples.... pituitary
Disease of the PROSTATE GLAND can affect the ?ow of URINE so that patients present with urological symptoms.
Prostatitis This can be either acute or chronic. Acute prostatitis is caused by a bacterial infection, while chronic prostatitis may follow on from an acute attack, arise insidiously, or be non-bacterial in origin.
Symptoms Typically the patient has pain in the PERINEUM, groins, or supra pubic region, and pain on EJACULATION. He may also have urinary frequency, and urgency.
Treatment Acute and chronic prostatitis are treated with a prolonged course of antibiotics. Patients with chronic prostatitis may also require anti-in?ammatory drugs, and antidepressants.
Prostatic enlargement This is the result of benign prostatic hyperplasia (BPH), causing enlargement of the prostate. The exact cause of this enlargement is unknown, but it affects 50 per cent of men between 40 and 59 years and 95 per cent of men over 70 years.
Symptoms These are urinary hesitancy, poor urinary stream, terminal dribbling, frequency and urgency of urination and the need to pass urine at night (nocturia). The diagnosis is made from the patient’s history; a digital examination of the prostate gland via the rectum to assess enlargement; and analysis of the urinary ?ow rate.
Treatment This can be with tablets, which either shrink the prostate – an anti-androgen drug such as ?nasteride – or relax the urinary sphincter muscle during urination. For more severe symptoms the prostate can be removed surgically, by transurethral resection of prostate (TURP), using either electrocautery or laser energy. A new treatment is the use of microwaves to heat up and shrink the enlarged gland.
Cancer Cancer of the prostate is the fourth most common cause of death from cancer in northern European males: more than 10,000 cases are diagnosed every year in the UK and the incidence is rising by 3 per cent annually.
Little is known about the cause, but the majority of prostate cancers require the male hormones, androgens, to grow.
Symptoms These are similar to those resulting from benign prostatic hypertrophy (see above). Spread of the cancer to bones can cause pain. The use of a blood test measuring the amount of an ANTIGEN, PROSTATE SPECIFIC ANTIGEN (PSA), can be helpful in making the diagnosis – as can an ULTRASOUND scan of the prostate.
Treatment This could be surgical, with removal of the prostate (either via an abdominal incision, total prostatectomy, or transurethrally), or could be by radiotherapy. In more advanced cancers, treatment with anti-androgen drugs, such as cyprotexone acetate or certain oestrogens, is used to inhibit the growth of the cancer.... prostate gland, diseases of
... thyroid gland, diseases of
The glands which provide substances for the development of the egg and the formation of the shell in trematodes and cestodes.... vitelline glands
Adeno-carcinoma. A hormone-related tumour in elderly men. Enlargement of the gland may be benign or carcinomatous. Fibrosis (hardening) may arise from inflammation. Obstruction of the outlet of the bladder through swelling of the gland (prostatism) may cause uraemia.
Symptoms. Bladder irritability; increased frequency during the night. Feeble forked stream of urine. Sometimes blood. Three quarters of such tumours are located in the posterior lobe of the prostate gland – readily accessible to the examining finger through the front wall of the rectum. Rectal examination reveals a hard rugged prostate. Cystoscopy confirms. Bone pains in the low back or pelvis reflect a stage where the tumour has already spread. Anaemia, weight loss, urgency.
All symptoms are worse by alcohol and spicy foods.
Harvard University scientists report: heavy consumption of animal fat, especially the fat in red meat appears to increase the chance that a man will develop advanced prostate cancer.
Of therapeutic value. Comfrey, Echinacea, Horsetail, Poke root, Thuja, Cornsilk, Goldenseal.
Tea. Combination. Comfrey leaves, Horsetail, Cornsilk. Equal parts. 2-3 teaspoons to each cup boiling water. Drink freely.
Formula No. 1. Echinacea 2; Comfrey 1; Poke root half; Thuja half. Mix. Dose: Powders: 500mg (two 00 capsules or one-third teaspoon). Liquid extracts: 1 teaspoon. Tinctures: 2 teaspoons. Thrice daily in water or cup of Cornsilk tea.
Formula No. 2. (Alternative) Echinacea 2; Goldenseal 1; Gotu Kola 1; Poke root half. Mix. Dose: Powders: 500mg (two 00 capsules or one-third teaspoon). Liquid extracts: 1 teaspoon. Tinctures: 2 teaspoons in water or cup of Cornsilk tea.
Bee pollen. Of value.
Garlic. Of value.
Diet. See: DIET – CANCER.
There is a very low incidence of prostate cancer in countries where Soya products are widely consumed – Soya contains a female hormone which is a protector factor.
Supplements. Morning and evening.
Vitamin A 7500iu or more. Large doses may be required. Vitamin C 1-2g. Vitamin E 200iu. Calcium 500mg. Selenium 100mcg. Zinc.
Study. Men with prostate cancer may not need to undergo radical prostatectomy (removal of the prostate gland). A 10-year follow-up study of men with early prostate cancer left untreated showed that 10 years later only 8.5 per cent of the 223 patients had died from prostate cancer. The survival rate of 86.8 per cent in the untreated group was nearly identical to a subgroup who met all the conditions for radical prostatectomy. (Journal of American Medical Association, 22/29 April 1992)
Commonly treated with female sex hormone or by orchidectomy.
It would appear that surgical removal of the gland offers little benefit, and possibly a disadvantage to patients wishing to leave well alone, particularly the elderly. Treatment by a general medical practitioner or oncologist. ... cancer – prostate gland
Traps in the lymphatic system that collect byproducts of body infection and which support the immune system in its role as body protector. ... lymph glands
A gland that discharges cellular material in addition to the fluid it secretes. The term is usually applied to the type of sweat glands that appear in hairy body areas after puberty. (See also eccrine gland.)... apocrine gland
A type of sweat gland.... eccrine gland
(submaxillary gland) one of a pair of *salivary glands situated below the parotid glands. Their ducts (Wharton’s ducts) open in two papillae under the tongue, on either side of the frenulum.... submandibular gland
see submandibular gland.... submaxillary gland
a simple coiled tubular *exocrine gland that lies in the dermis of the *skin. A long duct carries its secretion (*sweat) to the surface of the skin. Sweat glands occur over most of the surface of the body; they are particularly abundant in the armpits, on the soles of the feet and palms of the hands, and on the forehead.... sweat gland
see meibomian glands.... tarsal glands
the two pairs of glands that open at the junction of the vagina and vulva. The more posterior of the two are the greater vestibular glands (Bartholin’s glands); the other pair are the lesser vestibular glands. Their function is to lubricate the entrance to the vagina during coitus.... vestibular glands