Hypothyroidism Primer-Continued

David J. DeRose, MD, MPH As presented on the Three Angels Broadcasting Network’s “Health for a Lifetime”
Taped December 2005

Note: This material is designed to inform and educate. It represents the opinions of the author based on his understanding of current medical research and is not intended to be viewed as a replacement for medical evaluation, advice, diagnosis, or treatment. Because medicine is a constantly changing science that requires professional evaluation, neither the author nor the distributors of this material can take responsibility for any adverse consequences resulting from the application of this information. If the material in this handout disagrees with personalized information provided by your health care professionals, please follow the counsel of those health care providers—not this article.


15. I’m taking thyroid replacement therapy, should I avoid soy products and vegetables like broccoli and cabbage?

It’s true these foods have naturally occurring goitrogens (substances that interfere, to some extent, with thyroid function). However, these foods are also nutritional powerhouses, containing a variety of compounds with myriad health benefits including decreasing your risk of cancer and heart disease. Therefore, I usually feel uncomfortable telling people to avoid these foods. Especially if you already take a thyroid supplement and have a condition that is likely to be irreversible, avoidance of goitrogens is generally not in order.


16. My doctor says I have mild (subclinical) hypothyroidism. My TSH is 4.8; all my other thyroid tests are normal. My doctor says I could start taking low dose L-thyroxine. However, wouldn’t it be better to skip the medication and instead avoid soy and cruciferous vegetables?

It’s reasonable to consider dietary changes if you have mild or subclinical hypothyroidism. However, soy foods and vegetables like broccoli and cauliflower are not the foods that I’m most concerned about. If you really want to do yourself some good, try to decrease your exposure to man-made organic toxins. Dr. Theo Colburn recently reviewed data on a variety of common chemicals (like herbicides, pesticides, compounds used in plastics, etc.) and found that many impair either the production or activity of thyroid hormone.


17. How can I avoid these compounds that can adversely affect thyroid function?

I recommend “eating as low on the food chain as possible.” This means choosing plant products as much as possible. If you’re going to eat the flesh of an animal, bird, or fish, eat one that is only eating plant life—but even then, you may well be getting toxin exposures 5 to 10 times greater than eating the same amount of plant foods. The reason is that many of the worst toxins accumulate in the tissues of living creatures; the higher you go up the food chain, the more the toxins tend to accumulate. Ironically, therefore, when it comes to our thyroid, we may sometimes be better off drinking soy milk (containing some natural goitrogens) than cow’s milk (which may be contaminated with PCBs or other thyroid-impairing toxins).


18. I’m already a vegetarian, is there anything else I can do to avoid chemicals that may be affecting my thyroid?

Yes. Reassess your use of plastics for storing foods and beverages. Chemicals can leach out of plastic into the things we eat and drink. Heating things in plastic may be especially dangerous. For example, avoid using plastic or plastic wrap in microwaves. The best containers for storage and reheating appear to be those made of glass or other inert materials.


19. I’ve heard municipal water supplies (in addition to wells) can be contaminated with some of these compounds. Is this true?

Yes; frequent use of herbicides, pesticides, and other chemicals has tainted water supplies throughout much of our nation. To decrease exposure to these compounds, I recommend using a reverse osmosis system for the water you cook with or drink. You can also use a distiller—but it must be combined with a charcoal prefilter to effectively remove many organic compounds.


20. Can exercise affect thyroid function?

Physical activity generally improves metabolism, aiding in weight reduction, energy level, and bowel function. However, excessive exercise impairs thyroid function. Some research suggests sedentary people may often unwittingly impair thyroid function because their “moderate exercise” is too much for their out-of-shape body. Good exercise advice for your thyroid, therefore, includes “listening to your body” (slowing down when fatigued, etc.) and being wary of competitive activities where you may be tempted to overdo.


Selected References

• Bunevicius R, et al. Effects of thyroxine as compared with thyroxine plus triiodothyronine in patients with hypothyroidism. N Engl J Med. 1999 Feb 11;340(6):424-9.

• Colborn T. Neurodevelopment and endocrine disruption. Environ Health Perspect. 2004 Jun;112(9):944-9.

• Cooper DS. Combined T4 and T3 therapy–back to the drawing board. JAMA. 2003 Dec 10;290(22):3002-4.

• “Hypothyroidism” (Chapter 559) in Behrman: Nelson Textbook of Pediatrics, 17th ed., 2004 Elsevier.

• “Iodine and the synthesis and secretion of thyroid hormones” in Larsen: Williams Textbook of Endocrinology, 10th ed., Elsevier.2003.

• Lazarus JH. Thyroid disorders associated with pregnancy: etiology, diagnosis, and management. Treat Endocrinol. 2005;4(1):31-41.

• Pearce EN, et al. Effects of chronic iodine excess in a cohort of long-term American workers in West Africa. J Clin Endocrinol Metab. 2002 Dec;87(12):5499-502.

• “Thyroid Disorders” in Ferri: Practical Guide to the Care of the Medical Patient, 6th ed., 2004 Mosby, Inc.

• Weetman AP. Hypothyroidism: screening and subclinical disease. BMJ. 1997 Apr 19;314(7088):1175-8.