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| *''gonadotrophic adenomas'' secrete luteinizing hormone (]), follicle stimulating hormone (]) and their subunits | *''gonadotrophic adenomas'' secrete luteinizing hormone (]), follicle stimulating hormone (]) and their subunits | ||
| *''lactrotrophic adenomas'' or '']s'' secrete ] | *''lactrotrophic adenomas'' or '']s'' secrete ] | ||
| *''null cell adenomas'' do not secrete hormones | *''null cell adenomas'' do not secrete hormones, but may stain positive for ] | ||
| , but may stain positive for ] | |||
| ==Diagnosis== | ==Diagnosis== | ||
Revision as of 09:53, 19 December 2004
Pituitary adenomas are tumors that occur in the pituitary gland, and account for about 10% of intracranial neoplasms. They often remain undiagnosed, and small pituitary tumors are found in 6 to 24 percent of adults at autopsy.
Types
Pituitary tumors were, historically, classed as basophilic, 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 pitutary tumors is based on immunohistochemical staining:
- corticotrophic adenomas secrete adrenocorticotropic hormone (ACTH) and pro-opiomelanocortin (POMC)
- somatotrophic adenmoas secrete growth hormone (GH)
- thyrotrophic adenomas secrete thyroid stimulating hormone (TSH)
- gonadotrophic adenomas secrete luteinizing hormone (LH), follicle stimulating hormone (FSH) and their subunits
- lactrotrophic adenomas or prolactinomas secrete prolactin
- null cell adenomas do not secrete hormones, but may stain positive for synaptophsin
Diagnosis
The diagnosis is generally entertained either on the basis of visual difficulties arising from the compression of the optic nerve by the tumor, or on the basis of manifestations of excess hormone secretion: the specifics depend on the type of hormone. Tumors which cause visual difficulty are likety to be macroadenomas greater than 10 mm in diameter; tumors less than 10 mm are microadenomas.
The most common secretory pituitary tumor is the prolactinoma, which can cause galactorrhea, hypogonadism, amenorrhea, infertility, and impotence. GH-secreting tumors cause acromegaly (gigantism). Corticotrophic adenomas cause Cushing's disease. TSH-secreting adenomas can, rarely, cause hyperthyroidism. Tumors which secrete LH, FSH or TSH most often don't cause symptoms because of that hormone secretion. Some tumors secrete more than one hormone, the most common combination being GH and prolactin.
Prolactinomas are frequently diagnosed during pregnancy, when the hormone progesterone increases the tumor's growth rate.
Headaches may be present.
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. Prolactinomas are most often treated with bromocriptine, a dopamine agonist, and followed by serial imaging to detect any increase in size. Treatment where the tumor is large can be radiological (proton beam irradiation) or surgical, and patients generally respond well. Efforts have been made to use a progesterone antagonist for the treatment of prolactinomas, but so far have not proved successful.
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