hypophysectomy


Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.

Hypophysectomy

 

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

 [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.

hy·poph·y·sec·to·my

(hī'pof-i-sek'tŏ-mē),
Surgical removal of the hypophysis or pituitary gland.

hypophysectomy

(hī-pŏf′ĭ-sĕk′tə-mē)
n.
Surgical excision or destruction of the pituitary gland.

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.

hy·poph·y·sec·to·my

(hī-pof'i-sek'tŏ-mē)
Surgical removal of the hypophysis or pituitary gland.

hypophysectomy

Surgical removal or destruction of the pituitary gland. This may be necessary to remove a pituitary tumour or to prevent the secretion of pituitary hormones which encourage certain cancers of the breast, testicle or ovary.

hypophysectomy

the removal of the pituitary GLAND.
References in periodicals archive ?
Cercek, "Effects of hypophysectomy on vascular insulin-like growth factor-I gene expression after balloon denudation in rats," Atherosclerosis, vol.
Ovogenesis and its relation to the hypophysis: The effects of pregnancy hypophysectomy, thyroidectomy and hormone administration on the ovary of the rat.
Differential effect of hypophysectomy and growth hormane treatment on hepatic glucuronosyltransferases in male rats: evidence for an action at a pretranslational level for isoforms glucuronidating bilirubin.
The ovarian cycle of the watersnake Nerodia sipedon, and the effects of hypophysectomy and gonadotropin administration.
Although trans-sphenoidal hypophysectomy is recommended when there are visual deficiencies or evidence of tumour growth [5, 6], our second patient had a spontaneous reduction in tumour size (as did three of the 12 macro-adenomas in another series [10]).
Hypophysectomy may improve headaches in half of the cases, but can also paradoxically exacerbate them in 15% [20], or have no effect [24].
Hypophysectomy did not affect liver IGF-I mRNA levels in the euryhaline teleost, the tilapia, Oreochromis mossambicus.
Also, the reason for us to select preadipocytes for this study is, despite exposure to hormonal manipulations in vivo, such as estrogen treatment, hypophysectomy, or castration, preadipocytes cultured from various depots retain distinct cell-dynamic and biochemical responses relative to other depots (Kirkland et al., 1992; Lacasa et al., 1997).
In the ewe, disruption of LH secretion via hypophysectomy (surgical removal of the pituitary gland) on day 5 of the estrous cycle prevents growth of the CL as well as the rise in progesterone that marks the early luteal phase.
The patient underwent transsphenoidal hypophysectomy in the same year, and the adenoma was surgically removed.
Situations or procedures that pose an increased risk for accumulation of intracranial air include surgical interventions, such as burr holes (Gozur, 1987), posterior fossa surgery (Suri et al., 2000), craniofacial surgery (Clevens et al., 1999; Wanamaker et al., 1995; Sprague et al., 1999), transphenoidal hypophysectomy (Iplikcioglu et al., 2003), ventricular peritoneal shunt, and lumbar drain placement (Clevenger, 1990).
Sinuses with postsellar pneumatization have been considered to be technically less demanding for a transsphenoidal hypophysectomy as compared to the presellar pneumatization.