Hypophysectomy
hypophysectomy /hy·po·phys·ec·to·my/ (hi-pof″ĭ-sek´tah-me) excision of the pituitary gland (hypophysis).
hypophysectomy
hypophysectomy [hi-pof″ĭ-sek´to-me]
Definition
Hypophysectomy or hypophysis is the removal of the pituitary gland.
Purpose
The pituitary gland is in the middle of the head. Removing this master gland is a drastic step that was taken in the extreme circumstance of two cancers that had escaped all other forms of treatment. Cancers of the female breast and male prostate grow faster in the presence of sex hormones. It used to be that sex hormones could be suppressed only by removing their source, the glands that made them. After the gonads were removed, some cancers continued to grow, so other stimulants to their growth had to removed. At this point, some cancer specialists turned to the pituitary.
With the development of new therapeutic agents and methods, especially new ways to manipulate hormones without removing their source, this type of endocrine surgery has been largely relegated to history. However, tumors develop in the pituitary gland that require removal. Here, the idea is to remove the tumor but partially preserve the gland.
Description
There are several surgical approaches to the pituitary. The surgeon will choose the best one for the specific procedure. The pituitary lies directly behind the nose, and access through the nose or the sinuses is often the best approach. Opening the skull and lifting the frontal lobe of the brain will expose the delicate neck of the pituitary gland. This approach works best if tumors have extended above the pituitary fossa (the cavity in which the gland lies).
Newer surgical methods using technology have made other approaches possible. Stereotaxis is a three-dimensional aiming technique using x rays or scans for guidance. Instruments can be placed in the brain with pinpoint accuracy through tiny holes in the skull. These instruments can then manipulate brain tissue, either to destroy it or remove it. Stereotaxis is also used to direct radiation with similar precision using a gamma knife. Access to some brain lesions can be gained through the blood vessels using tiny tubes and wires guided by x rays.
Preparation
Pituitary surgery is performed by neurosurgeons deep inside the skull. All the patient can do to prepare is keep as healthy as possible and trust that the surgeon will do his usual excellent job. Informed surgical consent is important so that the patient is fully confident of the need for surgery and the expected outcome.
Aftercare
Routine post-operative care is required. In addition, pituitary function will be assessed.
Risks
The risks of surgery are multiple. Procedures are painstakingly selected to minimize risk and maximize benefit. Unique to surgery on the pituitary is the risk of destroying the entire gland and leaving the entire endocrine system without guidance. This used to be the whole purpose of hypophysectomy. After the procedure, the endocrinologist, a physician specializing in the study and care of the endocrine system, would provide the patient with all the hormones needed. Patients with no pituitary function did and still do quite well because of the available hormone replacements.
Normal results
Complete removal of the pituitary was the goal for cancer treatment. Today, removal of tumors with preservation of the gland is the goal.
Abnormal results
Tumors may not be completely removed, due to their attachment to vital structures.
Resources
Books
Biller, Beverly M. K., and Gilbert H. Daniels. "Neuroendocrine Regulation and Diseases of the Anterior Pituitary and Hypothalamus." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.
Key terms
Endocrine system — Group of glands and parts of glands that control metabolic activity. Pituitary, thyroid, adrenals, ovaries, and testes are all part of the endocrine system.
Hormone — A chemical made in one place that has effects in distant places in the body. Hormone production is usually triggered by the pituitary gland.
hypophysectomy /hy·po·phys·ec·to·my/ (hi-pof″ĭ-sek´tah-me) excision of the pituitary gland (hypophysis).
hy·poph·y·sec·to·my (h -p f  -s k t -m )n. Excision or destruction of the pituitary gland. |
hypophysectomy
[hīpof′əsek′təmē]
Etymology: Gk, hypo + phyein, to grow, ektomē, excision
surgical removal of the pituitary gland. It may be performed to slow the growth and spread of endocrine-dependent malignant tumors or to excise a pituitary tumor. The gland is removed only if other treatment, such as x-ray therapy, radioactive implants, or cryosurgery, fails to destroy all pituitary tissue. With general anesthesia, the gland is completely removed. Postoperative nursing care is as for a craniotomy. Levels of hormones, including thyroid-stimulating hormone, adrenocorticotropic hormone, and antidiuretic hormone, are monitored, and replacement therapy is begun as needed. Urinary output is measured every 2 hours for several days to monitor for diabetes insipidus, and an amount in excess of 300 mL in any 2-hour period is reported. The patient is closely monitored for early signs of thyroid crisis, Addisonian crisis, electrolyte imbalance, hemorrhage, hypothermia, and meningitis. hypophysectomize, v.
hypophysectomy [hi-pof″ĭ-sek´to-me]
surgical removal of part or all of the pituitary gland (hypophysis), usually a surgical procedure but sometimes done chemically by injection of alcohol into the sella turcica. The primary indication is as treatment of a pituitary tumor. Because of its influence on the adrenal cortex and other endocrine glands, removal of a portion of the pituitary gland can reduce the hypoglycemic effects of corticotropin, thyrotropin, and prolactin. Similarly, malignancies of the breast or prostate that are sensitive to hormones respond to removal of the pituitary hormones that stimulate the breast, ovaries, prostate, and adrenal glands. Elimination of these secondary hormones creates an environment hostile to the tumor cells. Hypophysectomy does not cure the malignancy but does help relieve the pain associated with growth of the tumor. The procedure is also under investigation as a treatment for diabetic retinopathy. 
A transsphenoidal hypophysectomy. This approach leaves normal pituitary tissue undisturbed. From Ignatavicius and Workman, 2002.
hypophysectomy
excision of the hypophysis, or pituitary gland. Surgical removal is a form of treatment for pituitary-dependent Cushing's syndrome in dogs.
hypophysectomy
Neurosurgery A procedure in which the hypophysis is destroyed or excised, mandated by a mass lesion in the sella turca, which requires permanent hormonal support. See Neuroablative procedure.
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