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THE INFORMATION WAS BELIEVED TO BE CURRENT ON MAY 22, 2000 AND WITH THE LAPSE OF TIME, CERTAIN OF THIS MATERIAL WILL BE OUTDATED.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 benefit.
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 Tissues
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 water retention.
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 tomography) scan.
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 disease.
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