Pituitary adenoma
Encyclopedia
Pituitary adenomas are tumor
s that occur in the pituitary gland
, and account for about 15% of intracranial neoplasms
. Tumors which exceed 10 mm in size are defined as macroadenomas, and those smaller than 10 mm are referred to as microadenomas. Most pituitary adenomas are microadenomas, which often remain undiagnosed, and have an estimated prevalence of 16.7% (14.4% in autopsy
studies and 22.5% in radiologic
studies).
, acidophilic
, or chromophobic on the basis of whether or not they took up the stains hematoxylin and eosin
. This classification has fallen into disuse, in favor of a classification based on what type of hormone
is secreted by the tumor (though tumors which do not secrete any active hormone ("non-functioning tumors") are still sometimes called "chromophobic").
At present, classification of pituitary tumors is based on plasma hormone levels or immunohistochemical staining, as given in table below. The "Percentage of hormone production cases" values are the fractions of adenomas producing each related hormone of each tumor type as compared to all cases of pituitary tumors, and does not directly correlate to the percentages of each tumor type because of smaller or greater incidences of absence of secretion of the expected hormone. Thus, nonsecretive adenomas may be either null cell
adenomas or a more specific adenoma that, however, remains nonsecretive.
. They are often discovered by computed tomography (CT) or MRI performed in the evaluation of unrelated medical conditions such as suspected head trauma, cancer staging
or in the evaluation of nonspecific symptoms such as dizziness and headache. It is not uncommon for them to be discovered at autopsy. In a meta-analysis
, adenomas were found in an average of 16.7% in postmortem studies, with most being microadenomas (<10mm); macrodenomas accounted for only 0.16% to 0.2% of the decedents.While pituitary microadenomas are generally considered benign the presence of a microadenoma has been positively identified as a risk factor for suicide in a postmortem study of suicide victims.
. The specifics depend on the type of hormone. Some tumors secrete more than one hormone, the most common combination being GH and prolactin.
In addition, a pituitary adenoma may present with visual field
defects, classically bitemporal hemianopia
. It arises from the compression of the optic nerve
by the tumor. The specific area of the visual pathway at which compression by these tumours occurs is at the optic chiasma.
The anatomy of this structure causes pressure on it to produce a defect in the temporal visual field on both sides, a condition called bitemporal hemianopia
. If originating superior to the optic chiasm
, more commonly in a craniopharyngioma
of the pituitary stalk
, the visual field defect will first appear as bitemporal inferior quadrantanopia, if originating inferior to the optic chiasm
the visual field defect will first appear as bitemporal superior quadrantanopia. Lateral expansion of a pituitary adenoma can also compress the abducens nerve, causing a lateral rectus palsy.
Also, a pituitary adenoma can cause symptoms of increased intracranial pressure.
Prolactinomas often start to give symptoms especially during pregnancy, when the hormone
progesterone
increases the tumor's growth rate.
Headaches may be present.
Tumors which cause visual difficulty are likely to be a macroadenoma greater than 10 mm in diameter; tumors less than 10 mm are microadenoma.
The differential diagnosis includes pituitary tuberculoma, especially in developing countries and in immumocompromised patients.
The diagnosis is confirmed by testing hormone levels, and by radiographic imaging of the pituitary (for example, by CT scan or MRI).
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s that occur in the pituitary gland
Pituitary gland
In vertebrate anatomy the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 g , in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity covered by a dural fold...
, and account for about 15% of intracranial neoplasms
Neoplasia
Neoplasm is an abnormal mass of tissue as a result of neoplasia. Neoplasia is the abnormal proliferation of cells. The growth of neoplastic cells exceeds and is not coordinated with that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the...
. Tumors which exceed 10 mm in size are defined as macroadenomas, and those smaller than 10 mm are referred to as microadenomas. Most pituitary adenomas are microadenomas, which often remain undiagnosed, and have an estimated prevalence of 16.7% (14.4% in autopsy
Autopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...
studies and 22.5% in radiologic
Medical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
studies).
Types
Pituitary tumors were, historically, classed as basophilicBasophilic
Basophilic is a technical term used by histologists. It describes the microscopic appearance of cells and tissues, as seen down the microscope, after a histological section has been stained with a basic dye. The most common such dye is haematoxylin....
, acidophilic
Acidophile
Acidophile may refer to:* Acidophile * Acidophile...
, or chromophobic on the basis of whether or not they took up the stains hematoxylin and eosin
Eosin
Eosin is a fluorescent red dye resulting from the action of bromine on fluorescein. It can be used to stain cytoplasm, collagen and muscle fibers for examination under the microscope. Structures that stain readily with eosin are termed eosinophilic....
. This classification has fallen into disuse, in favor of a classification based on what type of hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
is secreted by the tumor (though tumors which do not secrete any active hormone ("non-functioning tumors") are still sometimes called "chromophobic").
At present, classification of pituitary tumors is based on plasma hormone levels or immunohistochemical staining, as given in table below. The "Percentage of hormone production cases" values are the fractions of adenomas producing each related hormone of each tumor type as compared to all cases of pituitary tumors, and does not directly correlate to the percentages of each tumor type because of smaller or greater incidences of absence of secretion of the expected hormone. Thus, nonsecretive adenomas may be either null cell
Null cell
A null cell is a large granular lymphocyte without surface markers or membrane-associated proteins from B lymphocytes or T lymphocytes. Natural killer cells are usually null cells with surface marker CD 16 which bind to the Fc portion of the IgG, and thereby destroy it. NK-cells do immune...
adenomas or a more specific adenoma that, however, remains nonsecretive.
| Type of adenoma | Secretion | Staining | Pathology | Percentage of hormone production cases >- | lactotrophic adenomas or prolactinoma Prolactinoma A prolactinoma is a benign tumor of the pituitary gland that produces a hormone called prolactin. It is the most common type of pituitary tumor... s (most common) |
secrete prolactin Prolactin Prolactin also known as luteotropic hormone is a protein that in humans is encoded by the PRL gene.Prolactin is a peptide hormone discovered by Henry Friesen... |
acidophilic Acidophile (histology) An acidophile describes is a term used by histologists to describe a particular staining pattern of cells and tissues when using haematoxylin and eosin stains... |
galactorrhea Galactorrhea Galactorrhea or galactorrhoea is the spontaneous flow of milk from the breast, unassociated with childbirth or nursing.Contemporary Maternal-Newborn Nursing Care defines galactorrhea as "nipple discharge." -Causes:... , hypogonadism Hypogonadism Hypogonadism is a medical term for decreased functional activity of the gonads. Low testosterone is caused by a decline or deficiency in gonadal production of testosterone in males... , amenorrhea, infertility Infertility Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term... , and impotence |
>- | secrete growth hormone Growth hormone Growth hormone is a peptide hormone that stimulates growth, cell reproduction and regeneration in humans and other animals. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by the somatotroph cells within the lateral wings of the anterior... (GH) |
acidophilic Acidophile (histology) An acidophile describes is a term used by histologists to describe a particular staining pattern of cells and tissues when using haematoxylin and eosin stains... |
acromegaly Acromegaly Acromegaly is a syndrome that results when the anterior pituitary gland produces excess growth hormone after epiphyseal plate closure at puberty... (gigantism) |
>- | secrete adenocorticotropic hormone (ACTH) | basophilic Basophilic Basophilic is a technical term used by histologists. It describes the microscopic appearance of cells and tissues, as seen down the microscope, after a histological section has been stained with a basic dye. The most common such dye is haematoxylin.... |
Cushing's disease Cushing's disease Cushing's disease is a cause of Cushing's Syndrome characterised by increased secretion of adrenocorticotropic hormone from the anterior pituitary. This is most often as a result of a pituitary adenoma... >- | gonadotrophic adenomas |
secrete luteinizing hormone Luteinizing hormone Luteinizing hormone is a hormone produced by the anterior pituitary gland. In females, an acute rise of LH called the LH surge triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell-stimulating hormone , it stimulates Leydig cell... (LH), follicle-stimulating hormone Follicle-stimulating hormone Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotrophs of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone act... (FSH) and their subunits |
basophilic Anterior pituitary basophil An anterior pituitary basophil is a type of cell in the anterior pituitary which manufactures hormones.It is called a basophil because it readily takes up base, and typically stains a relatively deep blue or purple.... |
usually doesn't cause symptoms | >- | secrete thyroid-stimulating hormone Thyroid-stimulating hormone Thyrotrophin-stimulating hormone is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid gland.- Physiology :... (TSH) |
basophilic to chromophobic Anterior pituitary basophil An anterior pituitary basophil is a type of cell in the anterior pituitary which manufactures hormones.It is called a basophil because it readily takes up base, and typically stains a relatively deep blue or purple.... |
occasionally hyperthyroidism Hyperthyroidism Hyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous... , usually doesn't cause symptoms |
>- | do not secrete hormones | may stain positive for synaptophysin Synaptophysin Synaptophysin also known as the major synaptic vesicle protein p38 is a protein that in humans is encoded by the SYP gene.-Genomics:... |
25% of pituitary adenomas are nonsecretive |
Pituitary incidentalomas
Pituitary incidentalomas are pituitary tumors that are characterized as an incidental findingIncidental findings
Incidental findings are previously undiagnosed medical or psychiatric conditions that are discovered unintentionally and are unrelated to the current medical or psychiatric condition which is being treated or tests being performed...
. They are often discovered by computed tomography (CT) or MRI performed in the evaluation of unrelated medical conditions such as suspected head trauma, cancer staging
Cancer staging
The stage of a cancer is a description of the extent the cancer has spread. The stage often takes into account the size of a tumor, how deeply it has penetrated, whether it has invaded adjacent organs, how many lymph nodes it has metastasized to , and whether it has spread to distant organs...
or in the evaluation of nonspecific symptoms such as dizziness and headache. It is not uncommon for them to be discovered at autopsy. In a meta-analysis
Meta-analysis
In statistics, a meta-analysis combines the results of several studies that address a set of related research hypotheses. In its simplest form, this is normally by identification of a common measure of effect size, for which a weighted average might be the output of a meta-analyses. Here the...
, adenomas were found in an average of 16.7% in postmortem studies, with most being microadenomas (<10mm); macrodenomas accounted for only 0.16% to 0.2% of the decedents.While pituitary microadenomas are generally considered benign the presence of a microadenoma has been positively identified as a risk factor for suicide in a postmortem study of suicide victims.
Symptoms
Hormone secreting pituitary adenomas cause one of several forms of hyperpituitarismHyperpituitarism
Hyperpituitarism is the result of excess secretion of adenohypophyseal trophic hormones most commonly by a functional pituitary adenoma. Other causes are hyperplasias and carcinomas of the adenohypophysis, secretion by non-pituitary tumours and certain hypothalamic disorders.-Clinical...
. The specifics depend on the type of hormone. Some tumors secrete more than one hormone, the most common combination being GH and prolactin.
In addition, a pituitary adenoma may present with visual field
Visual field
The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...
defects, classically bitemporal hemianopia
Bitemporal hemianopsia
Bitemporal hemianopsia is the medical description of a type of partial blindness where vision is missing in the outer half of both the right and left visual field...
. It arises from the compression of the optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
by the tumor. The specific area of the visual pathway at which compression by these tumours occurs is at the optic chiasma.
The anatomy of this structure causes pressure on it to produce a defect in the temporal visual field on both sides, a condition called bitemporal hemianopia
Bitemporal hemianopsia
Bitemporal hemianopsia is the medical description of a type of partial blindness where vision is missing in the outer half of both the right and left visual field...
. If originating superior to the optic chiasm
Optic chiasm
The optic chiasm or optic chiasma is the part of the brain where the optic nerves partially cross...
, more commonly in a craniopharyngioma
Craniopharyngioma
Craniopharyngioma is a type of brain tumor derived from pituitary gland embryonic tissue, that occurs most commonly in children but also in men and women in their 50s and 60s....
of the pituitary stalk
Pituitary stalk
The pituitary stalk is the connection between the hypothalamus and the posterior pituitary....
, the visual field defect will first appear as bitemporal inferior quadrantanopia, if originating inferior to the optic chiasm
Optic chiasm
The optic chiasm or optic chiasma is the part of the brain where the optic nerves partially cross...
the visual field defect will first appear as bitemporal superior quadrantanopia. Lateral expansion of a pituitary adenoma can also compress the abducens nerve, causing a lateral rectus palsy.
Also, a pituitary adenoma can cause symptoms of increased intracranial pressure.
Prolactinomas often start to give symptoms especially during pregnancy, when the hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...
increases the tumor's growth rate.
Headaches may be present.
Diagnosis and workup
Diagnosis of pituitary adenoma can be made, or at least suspected, by a constellation of related symptoms presented above.Tumors which cause visual difficulty are likely to be a macroadenoma greater than 10 mm in diameter; tumors less than 10 mm are microadenoma.
The differential diagnosis includes pituitary tuberculoma, especially in developing countries and in immumocompromised patients.
The diagnosis is confirmed by testing hormone levels, and by radiographic imaging of the pituitary (for example, by CT scan or MRI).
Treatment
Treatment options depend on the type of tumor and on its size:- ProlactinomaProlactinomaA prolactinoma is a benign tumor of the pituitary gland that produces a hormone called prolactin. It is the most common type of pituitary tumor...
s are most often treated with bromocriptineBromocriptineBromocriptine , an ergoline derivative, is a dopamine agonist that is used in the treatment of pituitary tumors, Parkinson's disease , hyperprolactinaemia, neuroleptic malignant syndrome, and type 2 diabetes.- Indications :Amenorrhea, female infertility, galactorrhea, hypogonadism, and acromegaly...
or more recently, cabergolineCabergolineCabergoline , an ergot derivative, is a potent dopamine receptor agonist on D2 receptors. In vitro, rat studies show cabergoline has a direct inhibitory effect on pituitary lactotroph cells...
or quinagolideQuinagolideQuinagolide is a selective, D2 receptor agonist that is used for the treatment of elevated levels of prolactin....
which decrease tumor size as well as alleviates symptoms, both dopamine agonists, and followed by serial imaging to detect any increase in size. Treatment where the tumor is large can be with radiation therapyRadiation therapyRadiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...
or surgery, and patients generally respond well. Efforts have been made to use a progesterone antagonistReceptor antagonistA receptor antagonist is a type of receptor ligand or drug that does not provoke a biological response itself upon binding to a receptor, but blocks or dampens agonist-mediated responses...
for the treatment of prolactinomas, but so far have not proved successful. - Somatotrophic adenomas respond to octreotide, a long-acting somatostatin analogSomatostatinSomatostatin is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G-protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones.Somatostatin...
, in many but not all cases according to a review of the medical literature. Unlike prolactinomas, thyrotrophic adenomas characteristically respond poorly to dopamine agonist treatment. - Surgery is a common treatment for pituitary tumors. Trans-sphenoidal adenectomyTranssphenoidal surgeryTranssphenoidal surgery is a type of surgery in which surgical instruments are inserted into part of the brain by going through the nose and the sphenoid bone . Transsphenoidal surgery is used to remove tumors of the pituitary gland.- External links :* entry in the public domain NCI Dictionary of...
surgery can often remove the tumor without affecting other parts of the brain. Endoscopic surgery has become common recently.
External links
- Cancer.gov: pituitary tumors
- Cleveland Clinic: Evaluation and management of pituitary incidentalomashttp://www.ccjm.org/content/75/11/793.full#ref-3
- Case report of Bilateral Hemianopsia Due to Pituitary Adenoma. Clinical Cases and Images.
- Medical Illustration of Pituitary Adenomas by Frank H. Netter
- The Pituitary Foundation
- www.AcromegalyCommunity.com Emotional and communal support for those touched by Acromegaly
- - hipofizis.hu Hungarian Pituitary Tumors site