The calcitonin test is primarily used to help diagnose C-cell hyperplasia and medullary thyroid cancer, to evaluate the effectiveness of treatment, and to monitor patients for recurrence. It is also used to screen for medullary thyroid cancer in family members of patients with multiple endocrine neoplasia type 2 (MEN 2).

Stimulation tests are more sensitive than calcitonin measurements alone. This involves collecting a baseline sample, then giving the patient an injection of intravenous calcium or pentagastrin to stimulate calcitonin production. Several more blood samples are then collected over the next few minutes to measure the effect of the stimulation. Patients with early C-cell hyperplasia and/or medullary thyroid cancer will usually have very significant increases in their levels of calcitonin during this test.

Calcitonin levels may be ordered when you are suspected of having C-cell hyperplasia or medullary thyroid cancer. You or your doctor may notice a lump or swelling at the front of your neck. You may also experience other symptoms such as:

• Pain at the throat or front of your neck
• A change in your voice, hoarseness
• Difficulty swallowing or breathing
• Persistent cough not associated with a cold

A recent study also recommended measuring calcitonin before surgery in all patients with thyroid nodules, but not all clinicians agree. Stimulation tests may be ordered 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 medullary thyroid cancer or C-cell hyperplasia as early as possible. When someone has been treated for medullary thyroid cancer, calcitonin testing will usually be ordered at regular intervals to monitor treatment effectiveness and recurrence.

An elevated concentration of calcitonin means that excessive amounts are being produced. Significantly elevated levels of calcitonin are a good indicator of C-cell hyperplasia or medullary thyroid cancer; however, the doctor will use other procedures, such as a thyroid biopsy, scan, and ultrasound, to establish the diagnosis.

With successful treatment for medullary thyroid cancer (removal of the thyroid gland and often some surrounding tissues), calcitonin levels will usually fall to very low levels. If the values stay low over time, then it is likely that the treatment was effective. In some cases, calcitonin levels will fall but remain moderately elevated after treatment. This means that some calcitonin-producing tissue remains. 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 medullary thyroid cancer.

With medullary thyroid cancer and C-cell hyperplasia, other thyroid tests, such as T4, T3, and TSH, are usually normal while calcitonin levels are elevated.

Calcitonin levels also may be elevated with lung cancer, insulinomas, and other pancreatic tumors called VIPomas.