Thyroid Hormones and Cancer
Thyroid hormones are key players in normal growth, development and metabolism, as well as bone and brain development during pregnancy and infancy. They also seem to play a role in the development of some human cancer types.
Food and Thyroid Hormones
Foods rich in iodine:1
Zinc and vitamins A and E support the proper manufacture of thyroid hormones. Good sources:2
Three key hormones act and interact in complex patterns: TSH, T4 and T3:3
- Your pituitary gland produces TSH (thyroid stimulating hormone), which stimulates the thyroid gland to produce thyroid hormones.
- Your thyroid gland then produces T4 (thyroxine) and T3 (triiodothyronine), which circulate in your bloodstream.
- Your liver and kidneys convert T4 to T3 (triiodothyronine).
- Your thyroid also produces other hormones important for bone metabolism.
T4 and T3 control your metabolism—your heart rate and the supply of energy to your cells and nervous system for activity, growth or body heat.
Iodine is one of the main building blocks of both T4 and T3. For optimal thyroid function, appropriate amounts of iodine must be available to the thyroid. Good food sources of iodine are listed at right. Learn more in our Iodine therapy summary.
Thyroid Disorders and Cancer Risk or Development
Disorders in thyroid hormones are associated with increased risk of some cancer types:4
|Thyroid Disorder||Influence on Cancer Risk or Development|
|Low TSH levels|
|Elevated TSH levels||
|Higher free T4 levels (but not TSH levels)|
|Hyperthyroidism (overactive thyroid)||
|Hypothyroidism (underactive thyroid)||
|Induced hypothyroidism (intentionally created by medical treatment)|
Non-thyroidal illness syndrome (NTIS), also called euthyroid sick syndrome, occurs when thyroid function test results are abnormal without thyroid illness. NTIS may be associated with greater mortality and shorter overall survival with small-cell and non-small-cell lung cancer, glioma and lymphoma.5
Hormone levels and interactions may also support cancer progression by dampening immune responses.6
Thyroid hormone supplementation is associated with decreased risk of colorectal cancer, although T3 supplementation may interfere with colon cancer drug treatments. T4 and T3 can also interfere with the activity of bortezomib, a key drug in treating multiple myeloma.
The body's ability to use thyroid hormones—its bioavailability—can affect cancer development and spread. TSH can deliver signals to cells only if it can hook up with its receptors. The thyrotopin receptor gene (TSH-R, Genetics Home Reference) turns these receptors on and off. If this receptor is turned off (not expressed), thyroid hormones cannot bind and deliver their messages. Increasing the amount of thyroid hormone with supplementation will not improve the hormone’s effects on cancer progression. This has been validated in cell studies: human breast cancer tissues without expression of the thyrotropin receptor had more progressed cancer—higher pathologic grades—than those with TSH-R expression.7
Possibilities for Treatments
Hormones may stimulate cell growth through various pathways.8 Reducing thyroid hormones with chemical treatment or inhibiting their ability to bind to receptors are possible treatment pathways needing more investigation.9
Written by Laura Pole, RN, MSN, OCNS, and reviewed by Nancy Hepp, MS, and Maria Williams; most recent update on May 22, 2020.
- Endocrineweb: How Your Thyroid Works
- Medscape: Euthyroid Sick Syndrome
- Neil McKinney, BSc, ND: Naturopathic Oncology, 3rd Edition
- Lise Alschuler, ND, FABNO, and Karolyn Gazella: The Definitive Guide to Cancer, 3rd Edition
- Keith I. Block, MD: Life over Cancer: The Block Center Program for Integrative Cancer Treatment
- Gerald Lemole, MD; Pallav Mehta, MD; and Dwight McKee, MD: After Cancer Care