CHAPTER 8 Endocrine System^369
Thyroid Stimulating Hormone (TSH) Test
This blood test measures the level of TSH in the blood and is used to check for
thyroid gland problems. It may be done at the same time as tests to measure T3
and T4. Explain to the patient that this is a non-fasting blood test.
Thyroid Scintiscan (Thyroid Scan)
A radioactive substance is orally given to the patient, who returns at a designated
time for a thyroid scan. The test is done to assess nodules as either hot (function-
ing) which often indicates a goiter or a benign mass or cold (non-functioning)
which may indicate a cancer, thyroiditis or other disease process.
Before the test—Find out whether the patient has any allergies to iodine or shell-
fish. Speak to the practitioner about withholding thyroid medications before the
test. It is a non-invasive test.
Urinary Catecholamines
This test, a 24-hour urine test, measures the amount of the hormones epinephrine,
norepinephrine, and dopamine in the body. The test is done to assess for pheo-
chromocytoma (tumor of the adrenal gland) as the cause of elevated blood pressure.
Before the test—Instruct the patient to collect urine in a special container for a 24-
hour period. Explain to the patient that the test is started in the morning. Discard
the first voided specimen, then save subsequent specimens, ending with the first
voided specimen the following day. A preservative has been added to the container
and it must be refrigerated.
Vasopressin Challenge Test
This test is performed assess the ability of the kidneys to concentrate urine and
to help determine which type of diabetes insipidus is present. Vasopressin is
injected subcutaneously. Serum and urine samples are collected at 1 to 2-hour
intervals after the injection, and the osmolality of these samples is measured in
the laboratory.
Before the test—Explain to the patient that fluids are restricted the evening before
the test and the patient must be NPO after midnight. Any extra fluid or food intake
invalidates the test.