Thyroid cancer is the abnormal growth and uninhibited multiplication of cells of the thyroid gland. It gradually deteriorates the function of healthy cells, leading to complications in the body. The thyroid gland is part of the endocrine system, which regulates hormones in the body. The thyroid gland absorbs iodine from the bloodstream to produce thyroid hormones, which control a person’s metabolic rate. A healthy thyroid gland is barely palpable. If a tumor develops in the thyroid, it is felt as a lump in the neck. A tumor can be cancerous or benign. A tumor is considered malignant when it can grow and spread to other parts of the body. There is no single blood test that can accurately diagnose thyroid cancer. The results of thyroid function tests (determining the serum T3 and T4 and thyroid-stimulating hormone level) are usually normal in most patients with thyroid cancer. Normal thyroid blood tests do not rule out thyroid cancer.
Tests to diagnose thyroid cancer
- Tumor markers for thyroid cancers: These are the blood tests that detect certain substances. High levels of these substances are often seen in different types of thyroid cancers. However, these tests are not very sensitive and specific ways to diagnose thyroid cancer. They can be used during the treatment of cancer to see if the treatment is working.
- Table. The blood marker for thyroid cancers
Type of thyroid cancer
Medullary thyroid cancer (MTC)
Medullary thyroid cancer (MTC)
All types of thyroid cancer
- Radioiodine scan: This test can detect thyroid cancer and determine if cancer has spread. The patient is asked to swallow a pill containing a safe amount of radioactive iodine (radioiodine). Over a few hours, the thyroid gland absorbs the iodine. Then, the health care provider uses a special device to measure the amount of radiation in the gland. Areas with less radioactivity need more testing to confirm the presence of cancer.
- Imaging scans: Magnetic resonance imaging (MRI), computed tomography (CT) and positron emission tomography (PET) scans can detect thyroid cancer and cancer spread.
- Biopsy: During a fine-needle aspiration biopsy, the health care provider removes cells from the thyroid to test for cancer cells. A sentinel node biopsy can determine if cancer cells have spread to the lymph nodes. The health care provider may use ultrasound technology to guide these biopsy procedures.
Understanding the anatomy and function of the thyroid gland
The thyroid is a small, butterfly-shaped gland situated at the base of the front of the neck, just below Adam's apple.
Cells of the thyroid gland
Thyroid cancer starts when healthy cells in the thyroid change and grow out of control, forming a mass called a tumor. The thyroid gland contains two types of cells:
- Follicular cells: These cells are responsible for the production of thyroid hormone. Thyroid hormone controls the basic metabolism of the body, i.e., how quickly calories are burned. This can affect weight, slow down or speed up the heartbeat, raise or lower body temperature, influence how quickly food moves through the digestive tract, control the way muscles contract and control how quickly dying cells are replaced.
- C cells: These special cells of the thyroid make calcitonin, which is the hormone that participates in calcium metabolism.
What causes thyroid cancer?
Thyroid cancer is a rare type of cancer that affects the thyroid gland. It can occur in age group, although it is most common after 30 years of age, and its aggressiveness increases in older patients. Women are twice as more likely to develop it than men. The most common cause is the change that happens in the deoxyribonucleic acid (DNA) inside thyroid cells, which makes them grow uncontrollably and produce a lump. Other factors that increase the risk include
- Family history of thyroid cancer or thyroid disorders
- Radiation exposure during childhood, such as radiotherapy
- A bowel condition called familial adenomatous polyposis (FAP)
- Acromegaly, a rare condition where the body produces too much growth hormone
- A syndrome called MEN (multiple endocrine neoplasia), which causes multiple cancers in the body
- Low iodine intake
- Exposure to radioactive fallout from nuclear weapons or a power plant accident
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American Thyroid Association. Thyroid Cancer (Papillary and Follicular). https://www.thyroid.org/thyroid-cancer/