Hormone therapy for thyroid cancer

Hormones are substances that control some body functions, including how cells act and grow. Hormone therapy adds, blocks or removes hormones to slow or stop the growth of cancer cells that need hormones to grow. Hormone levels can be changed or blocked by drugs, surgery or radiation therapy.

Most people with thyroid cancer have hormone therapy. Your healthcare team will use what they know about the cancer and your health to plan the treatment.

If you have surgery to remove your thyroid (called a total thyroidectomy), you will need hormone therapy. Your thyroid normally makes a hormone called thyroxine (also called T4). Thyroxine helps control growth and development, and it helps maintain the body's normal metabolism. If the thyroid is removed, 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.

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

Levothyroxine (Synthroid, Eltroxin) is the standard hormone 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 papillary or follicular (including Hurthle cell) thyroid cancer from coming back (recurring). 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 of hormone therapy will depend mainly on the type of hormone therapy, the dose of a drug or combination of drugs, and your overall health. Tell your healthcare team if you have side effects that you think are from hormone therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Levothyroxine may cause these side effects:

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

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

Details on specific drugs change quite regularly. Find out more about sources of drug information and where to get details on specific drugs.