Calcitonin and Calcitonin Stimulation Tests

Synonym/acronym: Thyrocalcitonin, hCT.

Common use

To diagnose and monitor the effectiveness of treatment for medullary thyroid cancer.

Specimen

Serum (3 mL) collected in a gold-, red-, or red/gray-top tube. Place separated serum in a plastic transport tube within 2 hr of collection.

Normal findings

(Method: Chemiluminescent immunoassay)

Procedure	Medication Administered	Recommended Collection Times
Calcium and pentagastrin stimulation	Calcium, 2 mg/kg IV for 1 min, followed by pentagastrin 0.5 mcg/kg	4 calcitonin levels—baseline immediately before bolus; and 1 min, 2 min, and 5 min postbolus
Calcium stimulation	Calcium, 2 mg/kg IV for 1 min or 2.4 mg/kg IV push	4 calcitonin levels—baseline immediately before bolus; and 1 min, 2 min, and 5 min postbolus
Pentagastrin stimulation	Pentagastrin 0.5 mcg/kg	4 calcitonin levels—baseline immediately before bolus; and 1 min, 2 min, and 5 min postbolus

IV = intravenous.

	Conventional Units	SI Units (Conventional Units × 1)
Calcitonin Baseline
Male	Less than 10 pg/mL	Less than 10 ng/L
Female	Less than 5 pg/mL	Less than 5 ng/L
Maximum Response
5 min after calcium and pentagastrin stimulation
Male	8–343 pg/mL	8–343 ng/L
Female	Less than 39 pg/mL	Less than 39 ng/L
5 min after calcium stimulation
Male	Less than 190 pg/mL	Less than 190 ng/L
Female	Less than 130 pg/mL	Less than 130 ng/L
5 min after pentagastrin stimulation
Male	Less than 110 pg/mL	Less than 110 ng/L
Female	Less than 30 pg/mL	Less than 30 ng/L

Description

Calcitonin, also called thyrocalcitonin, is a hormone mainly secreted by the parafollicular or C cells of the thyroid gland in response to elevated serum calcium levels. The lungs and intestinal tract are other tissues that synthesize calcitonin to lesser degree. Calcitonin is also secreted by tumors of the C cells and is therefore, a useful marker for medullary thyroid cancer. Calcitonin participates in the regulation of calcium and phosphorus levels by antagonizing the effects of parathyroid hormone and vitamin D. It inhibits the activity of osteoclasts, so that calcium continues to be laid down in bone rather than be reabsorbed with phosphorus into the blood. Calcitonin also inhibits tubular reabsorption of calcium and phosphorus which increases their renal excretion. The net result is that calcitonin decreases the serum calcium level. Calcitonin is used therapeutically, by injection or nasal spray, in the case of osteoporosis to help slow down bone loss. The pentagastrin (Peptavlon) provocation test and the calcium pentagastrin provocation test are useful for diagnosing medullary thyroid cancer.

This procedure is contraindicated for

N/A

Indications

Assist in the diagnosis of hyperparathyroidism
Assist in the diagnosis of medullary thyroid cancer
Evaluate altered serum calcium levels
Monitor response to therapy for medullary thyroid carcinoma
Predict recurrence of medullary thyroid carcinoma
Screen family members of patients with medullary thyroid carcinoma (20% have a familial pattern)

Potential diagnosis

Increased in

Alcoholic cirrhosis (related to release of calcium from body stores associated with acute instances of malnutrition)
Cancer of the breast, lung, and pancreas (related to metastasis of calcitonin-producing cells to other organs)
Carcinoid syndrome (related to calcitonin-producing tumor cells)
C-cell hyperplasia (related to increased production due to hyperplasia)
Chronic renal failure (related to increased excretion of calcium and retention of phosphorus resulting in release of calcium from body stores; C cells respond to an increase in serum calcium levels)
Ectopic secretion (especially neuroendocrine origins)
Hypercalcemia (any cause) (related to increased production by C cells in response to increased calcium levels)
Medullary thyroid cancer (related to overproduction by cancerous cells)
MEN type II (related to calcitonin-producing tumor cells)
Pancreatitis (related to alcoholism or hypercalcemia)
Pernicious anemia (related to hypergastrinemia)
Pheochromocytoma (related to calcitonin-producing tumor cells)
Pregnancy (late) (related to increased maternal loss of circulating calcium to developing fetus; release of calcium from maternal stores stimulates increased release of calcitonin)
Pseudohypoparathyroidism (related to release of calcium from body stores initiates feedback response from C cells)
Thyroiditis (related to calcitonin-producing tumor cells)
Zollinger-Ellison syndrome (related to hypergastrinemia)

Decreased in

N/A

Critical findings

N/A

Interfering factors

Drugs that may increase calcitonin levels include calcium, epinephrine, estrogens, glucagon, oral contraceptives, pentagastrin, and sincalide.
Failure to follow dietary restrictions before the procedure may cause the procedure to be canceled or repeated.

Nursing Implications and Procedure

Pretest

Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
Patient Teaching: Inform the patient this test can assist in assessing the thyroid gland for disease or can monitor effectiveness of therapy.
Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
Obtain a history of the patient’s endocrine system, as well as results of previously performed laboratory tests and diagnostic and surgical procedures.
Note any recent procedures that can interfere with test results.
Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min; a few extra minutes are required to administer the stimulation tests. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
Direct the patient to fast for 10 to 12 hr before specimen collection. Protocols may vary among facilities.
Note that there are no fluid or medication restrictions unless by medical direction.
Prepare an ice slurry in a cup or plastic bag to have ready for immediate transport of the specimen to the laboratory. Prechill the collection tube in the ice slurry.

Intratest

Potential complications: N/A
Ensure that the patient has complied with dietary restrictions and pretesting preparations; ensure that food has been restricted for at least 10 to 12 hr prior to the procedure.
Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate tubes with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture; collect the specimen in a prechilled tube.
Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
The sample should be placed in an ice slurry immediately after collection. Information on the specimen label should be protected from water in the ice slurry by first placing the specimen in a protective plastic bag. Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
Instruct the patient to resume usual diet as directed by the HCP.
Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

Related tests include ACTH, biopsy thyroid, calcium, cancer antigens, catecholamines, CBC, gastrin stimulation test, magnesium, metanephrines, PTH, parathyroid scan, phosphorus, thyroglobulin, thyroid scan, TSH, US thyroid and parathyroid, and vitamin D.
Refer to the Endocrine System table at the end of the book for related tests by body system.