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8

NCCN Guidelines for Patients

®

:

Thyroid Cancer, Version 1.2017

1

Thyroid cancer

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

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:

†

†

T4 (thyroxine)

†

†

T3 (triiodothyronine)

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

follicular cells.

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

develop.

Cancer basics

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

(

d

eoxyribo

n

ucleic

a

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.