Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Calcitonin is a polypeptide hormone secreted by the parafollicular cells (also referred to as calcitonin cells or C cells) of the thyroid gland. The main action of calcitonin is the inhibition of bone resorption by regulating the number and activity of osteoclasts. Calcitonin is secreted in direct response to serum hypercalcemia and may prevent large oscillations in serum calcium levels and excessive loss of body calcium. However, in comparison to parathyroid hormone and 1,25-dihydroxyvitamin D, the role of calcitonin in the regulation of serum calcium in humans is minor. Measurements of serum calcitonin levels are, therefore, not useful in the diagnosis of disorders of calcium homeostasis.
Malignant tumors arising from thyroid C cells (medullary thyroid carcinoma: MTC) usually produce elevated levels of calcitonin. MTC is an uncommon malignant thyroid tumor, comprising less than 5% of all thyroid malignancies. Approximately 25% of these cases are familial, usually appearing as a component of multiple endocrine neoplasia type II (MENII, Sipple syndrome). MTC may also occur in families without other associated endocrine dysfunction, with similar autosomal dominant transmission as MENII, which is then called familial medullary thyroid carcinoma (FMTC). Mutations in the RET proto-oncogene are associated with MENII and FMTC.
Serum calcitonin concentrations are high in infants, decline rapidly, and are relatively stable from childhood through adult life. In general, calcitonin serum concentrations are higher in men than in women due to the larger C-cell mass in men. Serum calcitonin concentrations may be increased in patients with chronic renal failure, and other conditions such as hyperparathyroidism, leukemic and myeloproliferative disorders, Zollinger-Ellison syndrome, autoimmune thyroiditis, small cell and large cell lung cancers, breast and prostate cancer, mastocytosis, and various neuroendocrine tumors, in particular, islet cell tumors.
Aids in the diagnosis and follow-up of medullary thyroid carcinoma
Aids in the evaluation of multiple endocrine neoplasia type II and familial medullary thyroid carcinoma
Although most patients with sporadic medullary thyroid carcinoma (MTC) have high basal serum calcitonin concentrations, 30% of those with familial MTC or multiple endocrine neoplasia type II (MENII) have normal basal levels.
In completely cured cases following surgical therapy for MTC, serum calcitonin levels fall into the undetectable range over a variable period of several weeks. Persistently elevated postoperative serum calcitonin levels usually indicate incomplete cure. The reasons for this can be locoregional lymph node spread or distant metastases. In most of these cases, imaging procedures are required for further workup. Those individuals who are then found to suffer only locoregional spread may benefit from additional surgical procedures. However, the survival benefits derived from such approaches are still debated.
A rise in previously undetectable or very low postoperative serum calcitonin levels is highly suggestive of disease recurrence or spread, and should trigger further diagnostic evaluations.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test is not useful for evaluating calcium metabolic diseases.
Samples should not be taken from patients receiving therapy with high biotin or vitamin B7 doses (ie, >5 mg/day) until at least 12 hours following the last biotin administration.
Falsely elevated values may occur in serum from patients who have developed human antimouse antibodies or heterophilic antibodies.
In rare cases, interference due to extremely high titers of antibodies to analyte-specific antibodies, streptavidin, or ruthenium can occur.
Values obtained with different assay methods or kits may be different and cannot be used interchangeably. Test results cannot be interpreted as absolute evidence for the presence or absence of malignant disease.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
1 month: < or =34
2 months: < or =31
3 months: < or =28
4 months: < or =26
5 months: < or =24
6 months: < or =22
7 months: < or =20
8 months: < or =19.0
9 months: < or =17.0
10 months: < or =16.0
11 months: < or =15.0
12-14 months: < or =14.0
15-17 months: < or =12.0
18-20 months: < or =10.0
21-23 months: < or =9.0
2 years: < or =8.0
3-9 years: < or =7.0
10-15 years: < or =6.0
16 years: < or =5.0
17 years and older:
Males: < or =14.3
Females: < or =7.6
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Wells SA Jr, Asa SL, Dralle H, et al: Medullary Thyroid Carcinoma: management guidelines of the American Thyroid Association. American Thyroid Association Guidelines Task Force 2015 Jun;25(6):567-610
2. Griebeler ML, Gharib H, Thompson GB: Medullary thyroid carcinoma. Endocr Pract 2013 Jul-Aug;19(4):703-11
3. Richards ML: Familial syndromes associated with thyroid cancer in the era of personalized medicine. Thyroid 2010 Jul;20(7):707-13