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193. Tests regarding the adeno- and neurohypophysis
The pituitary gland or hypophysis is a small, bean-shaped gland located in the sella turcica.
The pituitary gland is divided into an anterior region (adenohypophysis) and a posterior
region (neurohypophysis). The hypothalamus regulates the pituitary gland, which in turn
transmits its own hormones that direct processes stimulating other endocrine glands to
produce different types of hormones.
The close proximity of the pituitary gland to major intracranial nerves and blood vessels, as
well as the vital hormonal control that the pituitary gland provides, can cause a pituitary
disorder with both hormonal and neurological symptoms.
Neurohypophysis secretes but mainly acts as a storage for the Antidiuretic Hormone (ADH,
vasopressin) and Oxytocin, both synthesized and secreted in the hypothalamus. This means
that damage to the stalk or pituitary alone does not prevent synthesis and release of ADH and
oxytocin.
Adenohypophysis secretes the following:
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Thyroid Stimulating Hormone (TSH)
Adrenocorticotrophic Hormone (ACTH)
Growth Hormone (GH)
Luteinizing Hormone (LH)
Follicle-stimulating hormone (FSH)
Prolactin (PRL)
Melanocyte stimulating hormone (MSH)
Tumors, inflammation, infection, and injury can cause the pituitary gland to malfunction and
result in either hypersecretion or hyposecretion of its hormones, cause headaches or vision
problems.
Testing the pituitary gland
Each axis of the hypothalamic-pituitary- system requires separate investigation
1. Blood levels of:
-Basal levels of certain hormones with long half-lives (e.g. T4 and T3) are especially useful.
-Basal samples for other hormones may be useful if interpreted with respect to normal ranges
for the time of day/month, diet or posture concerned. Examples are FSH, oestrogen and
progesterone (varying with time of cycle) and renin/aldosterone (varying with sodium intake,
posture and age).
-Stress-related hormones (e.g. Catecholamines, Prolactin, GH, ACTH and Cortisol) may
require samples to be taken via an indwelling needle some time after initial venopuncture;
otherwise, high levels may not be reliable.
-Blood levels of electrolytes (Sodium, Potassium, etc.), glucose, Creatinine, BUN and other.
2. Urine collections
-Collections over 24 hours have the advantage of providing a mean of a day's hormone
secretion and electrolytes in urine.
3.Stimulation and suppression tests
-Stimulation tests are used to confirm suspected deficiency, and suppression tests to confirm
suspected excess of hormone secretion. For example:
Cortrosyn Stimulation Test
-Adrenocorticotropic hormone (ACTH) is injected to stimulate the adrenal glands and blood
cortisol level is checked 60 minutes later.
-When pituitary disease impairs ACTH production, the adrenal glands lose their capacity to
secrete cortisol in response to stimulation.
Metyrapone Test
-Three grams of metyrapone are given to the patient at bedtime and blood is drawn the
following morning to check ACTH levels.
-Since metyrapone blocks adrenal hormone production, normal individuals respond by
producing large amounts of ACTH. Lack of response indicates pituitary disease affecting
ACTH production.
Insulin Tolerance Test
-In this test, insulin is injected to lower blood sugars (hypoglycemia).
-The normal response to hypoglycemia is release of ACTH and growth hormone (GH), which
counteracts low blood sugars. Patients deficient in GH and ACTH show no hormonal
response to hypoglycemia.
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4. Complete pituitary function test
-Measures the pituitary hormones before and after stimulation to find out which are working
normally and which are not. It includes three different stimulation tests: LHRH, TRH and
Insulin Stress Test.
-In some patients a prolonged Glucagon test may be performed with a short Synacthen test.
-If there is any suspicion of the involvement of the ADH hormone, Water Deprivation test is
performed.
http://www.dundee.ac.uk/medther/tayendoweb/hypopituitary.htm
5. Lateral skull X-ray
This may show enlargement of the fossa.
6. Visual fields testing
Common defects in pituitary disorders are upper-temporal quadrantanopia and bitemporal
hemianopia.
7. MRI and CT of the pituitary
Pituitary
Axis
hormone
Anterior pituitary
HP-ovarian
LH
FSH
HP-testicular
Growth
LH
FSH
GH
Prolactin
HP-thyroid
HP-adrenal
Prolactin
TSH
ACTH
Posterior pituitary
Thirst and
osmoregulation
Basal investigations
End-organ
Common dynamic
product/function tests
Other tests
Ovarian ultrasound
LHRH test
Estradiol
Progesterone (day
21 of cycle)
Testosterone
IGF-1
IGF-BP3
Insulin tolerance
test
Prolactin
Free T4, T3
Cortisol
-
Plasma/urine
osmolality
Water deprivation
test
Sperm count
LHRH test
GH response to
sleep, exercise or
arginine infusion
GHRH test
TRH test
Glucagon test
Insulin tolerance
test
Short synacthen
CRH test
(tetracosactide) test Metyrapone test
References
Kumar and Klark. (2008) Clinical Medicine .Elsevier Inc.
Hypertonic saline
infusion
Tayside University Hospitals NHS Trust. (2000) HYPOPITUITARY AND PITUITARY
REPLACEMENT HORMONES (online) Available from:
http://www.dundee.ac.uk/medther/tayendoweb/hypopituitary.htm
Tayside University Hospitals NHS Trust. (2000) COMPLETE PITUITARY FUNCTION TEST
(online) Available from: http://www.dundee.ac.uk/medther/tayendoweb/images/comppit.htm
Daniel Kelly, M.D. and Pejman Cohan, M.D. (2008) Pituitary Disorders. (online) Available
from: http://www.pituitary.org/disorders
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