|Information for the Public |
THIS INFORMATION WAS DEVELOPED BY DAVID M. COOK, M.D. AND MARY SAMUELS,
M.D. IT IS NOT INTENDED TO SUBSTITUTE FOR A FULL AND FRANK CONSULTATION
WITH QUALIFIED MEDICAL PERSONNEL, WHICH IS THE PRIMARY MEANS FOR A
PATIENT TO OBTAIN CARE AND TREATMENT. THE INFORMATION WAS BELIEVED
TO BE CURRENT ON MAY 22, 2000 AND WITH THE LAPSE OF TIME, CERTAIN
OF THIS MATERIAL WILL BE OUTDATED.
Glossary of Terms Used In Pituitary Diseases
by David M. Cook, M.D. and Mary Samuels, M.D.
Division of Endocrinology
Oregon Health Sciences University
There are a number of anatomical, hormonal and testing terms used
by pituitary gland specialists. You have heard about "lawyer
speak", and certainly physicians who take care of patients
with pituitary disease have their own language; which could be referred
to as "pituitary speak". This glossary in intended to
be used by patients and their families to help with understanding
pituitary PTS and the diagnostic and therapeutic tests which may
be associated with a pituitary problem. The authors hope it is of
Pituitary Hormones Affecting Target Glands
Thyroid stimulating hormone (abbreviated TSH); this hormone is produced
by the pituitary gland and is secreted (released) into the blood
stream, and stimulates the thyroid gland to make and secrete thyroid
hormone. Many kinds of pituitary disease cause deficiency of TSH,
which leads to thyroid hormone deficiency (hypothyroidism). Overproduction
of TSH from a pituitary tumor is also possible, but very rare. Such
tumors lead to thyroid hormone excess (hyperthyroidism).
Adrenocorticotrophic Hormone (abbreviated ACTH) ; this hormone
is produced by the pituitary gland and is secreted into the blood
stream, and stimulates the adrenal gland tissue to make and secrete
cortisol. Many kinds of pituitary disease cause deficiency of ACTH,
which leads to cortisol deficiency (hypoadrenalism). Overproduction
of ACTH from a pituitary tumor is also possible, and occurs in 10-15%
of tumors. This condition is called Cushing's Syndrome.
Luteinizing Hormone (abbreviated LH - also called ICSH); this hormone
is produced by the pituitary gland and is secreted into the blood
stream, and stimulates
ovary (female) or testes (male) to produce sex hormones such as
testosterone (males) and estrogen (females). This hormone also works
with another pituitary hormone called follicle-stimulating hormone
(abbreviated FSH) to stimulate the ovaries to produce eggs and the
testes to produce sperm cells. Deficiency of LH and FSH usually
occur together, and can be caused by many kinds of pituitary disease.
Overproduction of LH and/or FSH from a pituitary tumor is also possible,
although there are no specific symptoms in most cases.
Pituitary Hormones with Direct Effects on Particular Targeted
Prolactin (abbreviated PRL); this hormone has only one function
which is to stimulate breast tissue to produce milk. Although small
quantities are produced in both sexes it is only produced in significant
quantities following pregnancy and delivery. This hormone continues
only as long as a woman chooses to nurse her child. This hormone
is also produced by tumors of the pituitary gland referred to as
prolactinomas. These tumors, incidentally, are the most common of
the secreting tumors of the pituitary.
Growth Hormone (abbreviated GH); this hormone is produced by the
pituitary gland and is secreted into the blood stream and, unlike
the other pituitary hormones, exerts a direct effect on certain
tissues. This hormone affects multiple tissues including muscle,
fat and bone cells in a way that normalizes metabolism of these
tissues. Deficiency of GH is common in many types of pituitary disease.
Overproduction of GH is possible, and occurs in 10-20% of pituitary
tumors. Overproduction of GH during childhood causes gigantism,
while overproduction of GH during adulthood causes acromegaly.
Antidiuretic Hormone (abbreviated ADH); this hormone is produced
by the hypothalamus, a part of the brain just above the pituitary
gland, and is stored in the pituitary gland until it is needed.
It is secreted into the blood stream and affects the kidney to cause
Target Gland Hormones
Thyroid Hormones (abbreviated T4 and T3); these hormones are secreted
into the blood stream from the thyroid gland in response to stimulation
by pituitary TSH. T4 and T3 affect almost every tissue in the body
and regulate the speed (metabolic rate) of these tissues.
Cortisol (abbreviated F). This is a steroid hormone produced by
the adrenal glands in response to the pituitary hormone ACTH, and
affects many tissues in the body. Too much of this hormone is referred
to as Cushing's syndrome, too little of this hormone is referred
to as Addison's disease.
Estrogen. This hormone is produced by the ovaries in response to
LH and FSH. It stimulates certain tissues such as breast tissue,
uterus and fat cells and is responsible for maintaining bone, brain
and lipid metabolism.
Testosterone. This hormone is produced by the testes in males,
and is responsible for certain Metabolic effects which result in
hair growth, muscle development and influences sexual desire, referred
to as libido.
Magnetic Resonance Imaging (MRI). This revolutionary technique
does not use x-rays to create an image, but senses the fields of
different tissues to produce an image. Because of the magnet used
in this device, patients harboring metal devices such as pacemakers
or metal in a person's eye (welders are at risk for this) should
usually not undergo an MRI. This test also takes advantage of certain
tissues appearing different after a dye injection referred to as
gadolinium. (See the MRI pituitary web page to see different images
produced by an MRI of the pituitary in a normal patient and a patient
with a small or large pituitary tumor). If an MRI cannot be done,
an alternate way of imaging the pituitary gland is with a CT (computed
Visual field examination. This is a test performed by an ophthalmologist
that examines whether all "fields" of vision are normal.
For example, patients with pituitary tumors can have loss of peripheral
vision due to the growing tumor pressing on the nerves leading from
the eye. This peripheral vision loss may not be noticed by the patient,
but can be seen on visual field testing.
Pituitary Stimulation Tests
A stimulation test is usually performed when a deficiency
of a pituitary hormone is suspected. Because many pituitary hormones
are produced episodically and random sampling in blood may give
a low value in between normal episodic release, a stimulation test
is required to test the ability of the pituitary to release a specific
hormone. An example of a pituitary stimulation test is the use of
arginine to release growth hormone in patients with suspected growth
hormone deficiency. A rise in blood growth hormone is an expected
normal response to arginine infusion; failure to respond is abnormal
and proves the inability of the pituitary to release this hormone
normally. Stimulation tests are available for most of the pituitary
hormones, but should only be performed under certain circumstances,
and need to be interpreted by physicians experienced in pituitary
Pituitary Suppression Tests
This type of test is used when a pituitary hormone is questioned
to be in excess. The principle of a suppression test takes advantage
of normal secretion dynamics, that is, a normal response to an administered
drug or hormone is to "suppress" or go lower. Failure
to respond or "suppress" constitutes an abnormal response.
An example of a pituitary suppression test is to give oral glucose
and to observe blood growth hormone responses. A normal response
is to suppress growth hormone in blood after glucose ingestion.
An abnormal response is to not suppress or go lower. This test is
used when the endocrinologist is considering the diagnosis of acromegaly,
which is caused by a pituitary tumor making too much growth hormone.
Suppression tests are available for most of the pituitary hormones,
but should only be performed under certain circumstances, and need
to be interpreted by physicians experienced in pituitary disease