Thyroid cancer

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Hormonal therapy for thyroid cancer

Most people with thyroid cancer have hormonal therapy. Hormonal therapy is a treatment that adds, blocks or removes hormones. Hormones are substances that control some body functions, including the activity and growth of cells.

Your thyroid normally makes a hormone called thyroxine (also called T4 or free T4). Thyroxine helps control growth and development and helps maintain the body’s normal metabolism. If the thyroid is removed (called a total thyroidectomy), you will need to take drugs to replace thyroxine.

Thyroid-stimulating hormone (TSH) is made by the pituitary gland. It controls how the thyroid functions and grows, including when it makes thyroxine. TSH also controls the growth of thyroid cancer cells.

Hormonal therapy is used to control TSH, which in turn helps prevent cancer cells from growing and reduce the risk of thyroid cancer coming back, or recurring. This therapy is also called thyroid hormone therapy or TSH-suppression therapy.

Your healthcare team will consider your personal needs to plan your hormonal therapy. You may also receive other treatments before hormonal therapy is started.

Hormonal drug therapy used for thyroid cancer

Levothyroxine (Synthroid, Eltroxin) is the standard hormonal therapy for people who have a total thyroidectomy to treat thyroid cancer. This drug replaces the thyroxine that would normally be made by the thyroid.

Levothyroxine is also used to help prevent a recurrence of differentiated thyroid cancer (papillary or follicular carcinoma). Taking levothyroxine makes sure there is enough thyroid hormone in the body so the pituitary gland makes less TSH. Lowering the amount of TSH in the body may slow the growth of any remaining thyroid cancer cells.

Levothyroxine is usually given as a pill once a day. You will need to take it for the rest of your life. Doctors will regularly check thyroxine and TSH levels in the blood. This helps make sure that the right dose of levothyroxine is being given to keep TSH low without making thyroxine levels too high.

Side effects


Side effects can develop any time during, immediately after or a few days or weeks after hormonal therapy. Sometimes late side effects develop months or years after hormonal therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.

Side effects of hormonal therapy will depend mainly on the dose taken and your overall health. Some side effects of levothyroxine are:

  • fast or irregular heartbeat
  • weight loss
  • nervousness
  • shakiness, or tremors
  • sleep problems, such as insomnia
  • osteoporosis, especially the longer you take the drug

Tell your healthcare team if you have these side effects or others you think might be from hormonal therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them or adjust the dose of levothyroxine you are taking.

Information about specific cancer drugs


Questions to ask about hormonal therapy

Find out more about hormonal therapy and side effects of hormonal therapy. To make the decisions that are right for you, ask your healthcare team questions about hormonal therapy.


