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 those affected for recurrence. It is also ordered to screen for medullary thyroid cancer in family members of people with multiple endocrine neoplasia type 2 (MEN 2). C-cell hyperplasia and medullary thyroid cancer are two rare conditions in which excessive amounts of calcitonin are produced. C-cell hyperplasia is a benign condition that may or may not progress to become medullary thyroid cancer. Medullary thyroid cancer is malignant _ it can spread beyond the thyroid and can be difficult to treat if it is not discovered early. Stimulation tests are more sensitive than calcitonin measurements alone. This involves collecting a baseline sample, then giving a person 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. People with early C-cell hyperplasia and/or medullary thyroid cancer will usually have very significant increases in their levels of calcitonin during this test.
Blood tests can be done to look for the gene mutations found in familial medullary thyroid cancer (MTC). Because of this, most of the familial cases of MTC can be prevented or treated early by removing the thyroid gland. Once the disease is discovered in a family, the rest of the family members can be tested for the mutated gene.
If you have a family history of MTC, it is important that you see a doctor who is familiar with the latest advances in genetic counseling and genetic testing for this disease. Removing the thyroid gland in children who carry the abnormal gene will probably prevent a cancer that might otherwise be fatal.
If you have a lump in your neck that could be thyroid cancer, your doctor may do a biopsy of your thyroid gland to check for cancer cells. A biopsy is a simple procedure in which a small piece of the thyroid tissue is removed, usually with a needle, and then checked. Sometimes the results of a biopsy are not clear. In this case, you may need surgery to remove all or part of your thyroid gland before you find out if you have thyroid cancer.
Treatments for hyperthyroidism destroy the thyroid gland or block it from producing its hormones.
Antithyroid drugs such as methimazole (Tapazole) prevent the thyroid from producing its hormones.
A large dose of radioactive iodine damages the thyroid gland. You take it as a pill by mouth. As your thyroid gland takes in iodine, it also pulls in the radioactive iodine, which damages the gland.
Surgery can be performed to remove your thyroid gland.
If you have radioactive iodine treatment or surgery that destroys your thyroid gland, you will develop hypothyroidism and need to take thyroid hormone daily.
Test Method 1 : The actual diagnosis of thyroid cancer is made with a biopsy, in which cells from the suspicious area are removed and looked at under a microscope. However, this might not be the first test done if you have a suspicious lump in your neck. The doctor might order other tests first, such as blood tests, an ultrasound exam, or a radioiodine scan to get a better sense of whether you might have thyroid cancer. These tests are described below.
If your doctor thinks a biopsy is needed, the simplest way to find out if a thyroid lump or nodule is cancerous is with a fine needle aspiration (FNA) of the thyroid nodule. This type of biopsy can usually be done in your doctor's office or clinic.
Before the biopsy, local anesthesia (numbing medicine) may be injected into the skin over the nodule, but in most cases an anesthetic is not needed. Your doctor will place a thin, hollow needle directly into the nodule to aspirate (take out) some cells and a few drops of fluid into a syringe. The doctor usually repeats this 2 or 3 more times, taking samples from several areas of the nodule. The biopsy samples are then sent to a lab, where they are looked at under a microscope to see if the cells look cancerous or benign.
Bleeding at the biopsy site is very rare except in people with bleeding disorders. Be sure to tell your doctor if you have problems with bleeding or are taking medicines that could affect bleeding, such as aspirin or blood thinners.
This test is generally done on all thyroid nodules that are big enough to be felt. This means that they are larger than about 1 centimeter (about 1/2 inch) across. Doctors often use ultrasound to see the thyroid during the biopsy, which helps make sure they are getting samples from the right areas. This is especially helpful for smaller nodules. FNA biopsies can also be used to get samples of swollen lymph nodes in the neck to see if they contain cancer.
Sometimes an FNA biopsy will need to be repeated because the samples didn't contain enough cells. Most FNA biopsies will show that the thyroid nodule is benign. Rarely, the biopsy may come back as benign even though cancer is present. Cancer is clearly diagnosed in only about 1 of every 20 FNA biopsies.
Sometimes the test results first come back as ñsuspiciousî or ñof undetermined significanceî if FNA findings don't show for sure if the nodule is either benign or malignant. If this happens, the doctor may order tests on the sample to see if the BRAF or RET/PTC genes are mutated (changed). Finding these changes makes thyroid cancer much more likely, and may also play a role in determining the best treatment for the cancer.
If the diagnosis is not clear after an FNA biopsy, you might need a more involved biopsy to get a better sample, particularly if the doctor has reason to think the nodule may be cancerous. This might include a core biopsy using a larger needle, a surgical ñopenî biopsy to remove the nodule, or a lobectomy (removal of half of the thyroid gland). Surgical biopsies and lobectomies are done in an operating room while you are under general anesthesia (in a deep sleep). A lobectomy can also be the main treatment for some early cancers, although for many cancers the rest of the thyroid will need to be removed as well (during an operation called a completion thyroidectomy).