You might never think about your thyroid unless something goes wrong. Nonetheless, this often under-appreciated gland has a powerful effect on how well you feel. Too little thyroid hormone, and you are likely to feel lethargic and weak. If your thyroid puts out too much hormone, however, you may feel uncomfortably “wired” and have a hard time sleeping. Can you optimize your thyroid function?

Getting the Thyroid Up to Speed:

Q. I just got my annual thyroid test results. My doctor said my thyroid function was “low normal,” whatever that means.

Unfortunately, I feel sluggish most days and can barely get going in the morning. I have gained about 10 pounds that I cannot shed despite cutting back on portions. Is it possible that I need to increase my dose of levothyroxine to be more “normal?”

A. It is possible that a higher dose of levothyroxine will improve your thyroid function. However, you will need to work with your doctor on this. The thyroid gland is tiny but mighty, at least when it is functioning properly. It regulates metabolism and has an impact on every tissue in the body from your brain to your toenails. 

How Can You Measure Thyroid Function?

Physicians sometimes rely on a single blood test called the TSH to evaluate thyroid function. TSH stands for Thyroid Stimulating Hormone. This brain chemical indicates whether the pituitary gland in the brain is trying to get your thyroid gland to pump out more hormone or less. When it wants the gland to work harder, it sends more. Consequently, a high TSH value indicates poor thyroid function, or hypothyroidism. Conversely, a very low level of TSH suggests that the thyroid is producing too much hormone and the brain doesn’t want it to make any more. This indicates hyperthyroidism.

What Can You Do About Hypothyroidism?

An underactive thyroid gland can make you feel lethargic and interfere with your ability to exercise and lose weight. You might ask your doctor to review a more complete thyroid panel to see whether increasing the dose of your thyroid hormone replacement (levothyroxine) would be helpful. If that doesn’t prove helpful, you might request a trial of a regimen that includes some T3 (triiodothyronine) along with the T4 (levothyroxine). Although many endocrinologists are not convinced this is necessary, some patients appear to feel better when they get both hormones (Endocrine Practice, Sep-Oct. 2012).

What Else Can You Do to Help Your Thyroid Function Properly?

One thing your doctor might not have mentioned is that coffee can interfere with the proper absorption of Synthroid and possibly some generic formulations of levothyroxine (Thyroid, March 2008). To avoid this interaction, you should wait at least 30 minutes after taking your thyroid tablet before you have any coffee. Drinking milk with your pill also reduces absorption (Thyroid, April 2018).

If this complicates your schedule too much, consider taking your medication at bedtime. A double-blind study showed this is a viable alternative (Archives of Internal Medicine, Dec. 13, 2010). 

In fact, the investigators concluded: 

“Levothyroxine taken at bedtime significantly improved thyroid hormone levels.”

What About Diet?

Many people have heard that soy products like tofu are an important part of a healthy diet. Post-menopausal women may be eating tofu or drinking soy milk to reduce their hot flashes. Will a soy-rich diet affect thyroid function?

Confusion over Soy and Thyroid Function:

Q. I am searching for information on a link between hypothyroidism severity and soy products. There is a lot of talk about the benefits and risks of soy these days…it’s confusing! I read that I needed to increase soy post hysterectomy, but have also read that thyroid issues can increase post-hyst.

Now I have read that  soy can negatively affect the thyroid. Sshheesh! I can’t win! Also, any good suggestions for post-hyst health?

Too Much Soy in the Diet?

A. The soy-thyroid confusion continues. We just met with a physician who described a patient who had started consuming a fair amount of soy. This woman was eating soy sausage for breakfast, eating yogurt made of soy, and also consuming tempeh and tofu. He said that her thyroid function dropped dramatically and her TSH levels went up accordingly. When she stopped consuming so much soy, her TSH levels returned to normal and her thyroid hormone dose was lowered.

That is just one case, but it does suggest that some people are quite sensitive to soy. Some years ago we discovered a study in the journal Environmental Health Perspectives (June 2002, Suppl. 3) that dealt with this question head on. The researchers found that compounds in soy can inactivate an enzyme important for thyroid function. Ever since then, scientists have been arguing about the practical importance of this discovery. People low in iodine seem especially susceptible.

Should You Be Eating More Soy?

It is sad that there has been so little good research undertaken to answer your important question, especially since millions of women are now consuming huge quantities of soy products and even taking soy supplements. We suggest that you monitor your thyroid function with periodic blood tests to determine what is happening. More recent research has shown that people with questionable thyroid function may become frankly hypothyroid after consuming soy phytoestrogens (Journal of Clinical Endocrinology and Metabolism, May 2011). On the other hand, the most recent research shows that people getting high doses of soy isoflavones have a temporary increase in their reverse T3 (Frontiers in Endocrinology, Nov. 22, 2018).

Diane reported her experience:

“I definitely had soy interfere with my thyroid function a few years ago. I’ve been on the same dose of Armour thyroid for a decade yet started feeling hypothyroid (getting cold, especially after eating, and not being able to warm up) after I started drinking a couple of glasses of soy milk everyday. I stopped the soy milk, and my hypothyroid symptoms went away. Now I stay away from all soy. I think I could tolerate small amounts here and there, but not a lot every day.”

Learn More:

You can learn more about the symptoms of under- and overactive thyroid glands, how to interpret test results and how these conditions are treated in our eGuide to Thyroid Hormones.

Our most recent podcast on these topics was Show 1162: How to Treat Common Thyroid Problems, with Dr. David Cooper, director of the Thyroid Clinic at Johns Hopkins University. You may also wish to listen to our interviews with Mary Shomon and Dr. Antonio Bianco in our Show 1096: What You Need to Know About Treating Thyroid Disease.

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