NCCN Guidelines for Patients
Thyroid Cancer, Version 1.2017
The thyroid | Cancer basics
Learning that you have cancer can be
overwhelming. It is helpful to start talking
with your medical team about upcoming
tests and treatment options. Part 1 starts
with information about the thyroid. This
chapter then shares what doctors know
about cancer that starts here.
The thyroid is a gland in the neck. It is found below
the Adam’s apple (thyroid cartilage) in the lower,
front part of your neck. The thyroid is shaped like a
butterfly. It has two lobes, right and left, with a thin
piece of tissue that connects the lobes. This thin
tissue is called the isthmus.
The thyroid can often be felt just below your Adam’s
apple on either side of the trachea. Parathyroid
glands are small glands that are found in the neck
near the thyroid. These glands control the amount of
calcium in your bloodstream.
See Figure 1.
How it works
Glands are organs that make fluids or hormones. The
thyroid gland makes thyroid hormones. Hormones
are chemicals in the body that activate cells or
organs. The thyroid uses a mineral from your diet
called iodine to produce these hormones. Certain
foods and iodized salt contain iodine.
The thyroid contains several different kind of cells
that make more than one hormone. The thyroid
makes two other main hormones known as:
These hormones control your body temperature,
blood pressure, heart rate, and metabolism (how fast
food becomes fuel for your body), and many other
body functions. These hormones are made by the
The thyroid also makes calcitonin, which has a small
effect on how much calcium you have in your blood.
Calcitonin is made by C cells. The follicular and the C
cells that make these hormones can become cancer.
Thus, the thyroid gland has different cancers that can
Cancer is a disease that starts in the cells of your
body. Cells are the building blocks of tissue in the
body. The human body contains trillions of cells. DNA
cid) is found within each cell and
controls the cells, instructing them on what to do.
The coded instructions for your cells found in DNA
are called genes. These instructions are the genetic
code that tells cells what to become (eg, heart, lung,
thyroid) and what to do (eg, pump blood, absorb
oxygen, make hormones).
Normal cells grow and divide and repeat the process
over and over again. Normal genes tell cells that
they are supposed to die when they become old or
damaged. If they don’t die, and new cells start to
form, this growth can get out of control. Abnormal
out-of-control growth can be caused by a problem
with the genes, and can lead to the growth of a
solid mass of cells called a tumor. Some tumors are
malignant (cancer). Solid tumors can grow anywhere
in the body and can affect the way the body works.
See Figure 2.