To help diagnose and monitor C-cell hyperplasia and medullary thyroid cancer (MTC); to screen those at risk for MTC because of multiple endocrine neoplasia type 2 (MEN 2) or other mutations in the RET oncogene
If your doctor suspects that you have MTC, if you are being treated for MTC, or if a family member has MTC or MEN 2
Ideally after an overnight fast, a blood sample is obtained by inserting a needle into a vein in the arm. The sample may need to be collected on ice and must be sent to the laboratory for immediate processing.
After an overnight fast, a blood sample is obtained by inserting a needle into a vein in the arm. The sample may need to be collected on ice and must always be transferred to the laboratory for immediate processing.
It is important that the person taking the sample follows the instructions of the local laboratory as different laboratories may require different specimen types. Please contact the local laboratory for details.
This test measures the amount of calcitonin in the blood. The function of calcitonin in the human body is unknown; what is known is that it is a hormone produced by C-cells in the thyroid. The thyroid is a small butterfly-shaped gland that lies over and flat against the windpipe in the throat. It produces several hormones, primarily T4 (thyroxine) and T3 (triiodothyronine), that help control the rate of metabolism.
In two rare conditions, C-cell hyperplasia and medullary thyroid cancer (MTC), excessive amounts of calcitonin are produced. C-cell hyperplasia is a benign condition that may or may not progress to become MTC. MTC is malignant; it can spread beyond the thyroid and can be difficult to treat if it is not discovered early.
About 75-80% of MTC cases are sporadic, but about 20-25% are related to an inherited mutation in the RET oncogene that leads to multiple endocrine neoplasia type 2 (MEN 2), a syndrome associated with several related diseases, including MTC. The altered RET oncogene is inherited in an autosomal dominant fashion. This means that only 1 copy of the mutated oncogene, from either your father or mother, is required to have a greatly increased risk of developing MTC. Most cases of sporadic MTC develop when patients are in their 40s or 50s and the prevalence is higher in women, but inherited MTC affects both sexes equally and can occur at an early age.
How is it used?
The calcitonin test is primarily used to help diagnose C-cell hyperplasia and medullary thyroid cancer (MTC), to evaluate the effectiveness of treatment for MTC, and to monitor patients for recurrence of MTC following treatment. It is also used to screen for MTC in family members of patients with MEN 2. Baseline calcitonin results may be useful if MTC is suspected but, it is not routinely recommended for all thyroid nodules.
Tests which attempt to stimulate the levels of calcitonin are more sensitive than calcitonin measurements alone. These tests involve collecting a sample before stimulation, then giving the patient an injection of intravenous calcium and/or pentagastrin to stimulate calcitonin production. Several more blood samples are then collected over the next few minutes to gauge the effect of the stimulation. Patients with early C-cell hyperplasia and/or MTC will usually have very significant increases in their levels of calcitonin during this test. This test is also performed to diagnose MTC pre-operatively in relatives of patients with familial MTC, when there are false-positive baseline calcitonin levels or when the levels are only slightly raised.
When is it requested?
Calcitonin may be requested when a patient is suspected of having C-cell hyperplasia or MTC, but not with all thyroid nodules. Stimulation tests may be used when a patient has indeterminate or normal calcitonin results but clinical suspicions remain. These tests may be regularly performed on family members of patients who have MEN 2, starting at an early age, in order to detect MTC or C-cell hyperplasia as soon as it occurs. When someone has been treated for MTC, calcitonin testing will usually be requested at regular intervals to monitor treatment effectiveness and recurrence. Immediate postoperative samples are collected no earlier than 10 days after thyroidectomy and it should also be fasting samples if possible. In long term follow up, calcitonin is measured usually 6 months after surgery.
What does the test result mean?
An elevated concentration of calcitonin means that excessive amounts are being produced. Significantly elevated concentrations of calcitonin are a good indicator of C-cell hyperplasia or MTC; however, the doctor will use other procedures, such as a thyroid biopsy, scan, and ultrasound, to confirm the diagnosis.
With successful treatment for MTC (removal of the thyroid gland and often some surrounding tissues), calcitonin will usually fall to very low concentrations. If the values stay low over time, then it is likely that the treatment was effective. In some cases, calcitonin will fall but remain moderately elevated after treatment. This means that some calcitonin-producing tissue remains. It will also depend upon baseline calcitonin before the surgery and the stage of the tumour at the presentation. Doctors will monitor calcitonin and watch for increases over time. If calcitonin levels begin to rise, then it is likely that there is a recurrence of MTC.
Is there anything else I should know?
Why isn't calcitonin testing performed as a routine screen?
If my thyroid is removed, will I need to replace my calcitonin?
Is calcitonin ever used as a supplement?
Yes, but in a totally different context. Because it inhibits bone loss when given in very large doses, calcitonin is sometimes given as a drug to people who have osteoporosis. It helps maintain bone density and has a pain-relieving effect on bone.