Page 343 - Critical Care Nursing Demystified

328 CRITICAL CARE NURSING DeMYSTIFIED

TSH (thyroid-stimulating hormone) – Determines if a problem is caused by
the thyroid gland itself or is due to a secondary problem of the anterior pi-
tuitary gland. No fasting is required for this test. Normal values are 2 to 5.4
mU/mL. TSH levels will be very high in cases of hypothyroidism, in an effort
to stimulate the failing thyroid gland, and very low in cases of hyperthyroid-
ism, in an effort to reduce thyroid hormone output.

Total T4/L-thyroxine serum concentration – Measures both the free T4 and TBG
(thyroxine-binding hemoglobin). Normal value for adults is 4 to 12 ug/dL. In-
fants, children, pregnant women and those taking oral contraceptives have higher
results such as 15 to 16.5 ug/dL. Fasting is recommended for this test. Results
will be elevated with hyperthyroidism and liver disease and decreased with hy-
pothyroidism. It should be noted if the patient is already taking a thyroid prepa-
ration. Propranolol and Dilantin can also interfere with accuracy of test results.
T3 (triiodothyronine serum concentration) – This measurement is needed
when a person has a normal T4 but presents with clinical symptoms of
thyrotoxicosis. T3 value will be elevated with thyrotoxicosis while other test
results remain within normal limits. Fasting prior to testing is recommended.
Normal adult value is 110 to 230 ng/dL.
Thyroid scan and RAI (radioactive iodine uptake) – A thyroid scan in conjunc- Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.
tion with an RAI is done to identify and diagnose hypo- and hyperthyroidism,
nodules, cancer of the thyroid, and ectopic thyroid tissue. An RAI test mea-
sures the rate of iodine uptake by the thyroid gland after giving iodine 123
intravenously, by capsule, or by solution. Gamma rays are measured as they are
released from the breakdown of the tracer in the thyroid gland. Radioactivity
of the thyroid gland, neck, and mediastinum is visualized. A normal result will
show even distribution of the radioactive iodine in the thyroid gland. Images
visualized as cold nodules will aid in confirming cancer of the thyroid gland.

Ultrasound – A noninvasive study that utilizes high-frequency sound waves
to produce an image of the thyroid gland. Cysts, masses, and enlargement of
the thyroid gland can be detected.
Fine-needle biopsy – The diagnostic tool of choice to evaluate a thyroid mass
or detect a malignancy of a thyroid nodule. Cytology of biopsied material will
be positive for cancer cells even if thyroid tests were previously normal.

3 Patient Assessment
The astute nurse will be able to distinguish the physical differences between
hypo- and hyperthyroidism by obtaining a detailed health history and thorough
physical assessment. A health history should reveal prior or current use of a