John Davis

Written by John Davis


Thyroid Imbalance in Runners: A Look at the Impact of Training on Thyroid Levels

A thyroid disorder can be a vexing problem for a runner.

The initial symptoms of a problem with thyroid hormone levels are quite vague, and even once it’s diagnosed, thyroid levels have to be closely monitored and managed to ensure good health.

The thyroid hormone essentially sets the “speedometer” for many of the body’s intrinsic functions.

  • When thyroid hormone levels are too high, a condition termed hyperthyroidism, you will experience symptoms like weight loss, tremors, anxiety, and a racing heart rate.
  • In hypothyroidism, when thyroid hormone levels are too low, you might gain weight, become constipated, be overly sensitive to cold temperatures, and feel fatigued or depressed.

In both cases, thyroid disorders can be diagnosed by a blood test.  Paradoxically, people with both conditions usually end up taking thyroid hormones: hypothyroidism is treated by directly supplementing the body’s depressed production of the hormone with a synthetic form, while hyperthyroidism is treated by attacking the thyroid gland itself, which eventually slows or stops its thyroid hormone production after treatment.

Since a healthy thyroid gland regulates levels of thyroid hormones dynamically to respond to myriad changes in the body, people taking synthetic thyroid hormones often have to modulate their dosage over time.  As we’ll soon see, there is evidence that this can become a particularly thorny problem in athletes due to the unique stresses they subject their bodies to.

Because the thyroid can be such a difficult problem for runners, this week’s article digs into the scientific literature to see what we can learn about managing thyroid disorders in runners.

The research supporting thyroid treatment and running

While there is not much in the way of authoritative reviews on thyroid conditions in athletes, it’s clear that we as runners aren’t immune to them. Many top-level elite athletes, including Galen Rupp and Adam Goucher—two of the best American 5k and 10k runners in recent history— reportedly have hypothyroidism. Approximately 5 percent of the general population is affected. While most of these cases are termed “subclinical,” meaning that the levels of thyroid hormone are only borderline-low, the medical community debates about whether treatment is necessary.

  • A 2001 review study by Michael McDermott and Chester Ridgway at the University of Colorado Health Sciences Center argues strongly that mild thyroid failure, the cause of subclinical hypothyroidism, should be treated in order to prevent many of the health problems associated with lowered thyroid hormone levels later in life.
  • On the other hand, a 2007 Cochrane Collaboration meta-analysis found only marginal benefits when subclinical hypothyroidism was treated.
  • For unknown reasons, women are about four times more likely to suffer from hypothyroidism (both clinical and subclinical).

The impact of training on thyroid levels

When it comes to thyroid levels in runners, there’s no solid understanding of the effects of endurance training.  A few small studies which have examined the effects of endurance exercise on thyroid hormone levels have indicated that training can at least influence thyroid hormone profiles.

A 1982 study of 29 healthy women running about 14 miles a week first tested their thyroid levels, then instructed them to increase their mileage to 30 miles a week for two weeks. After the increase in mileage, their hormone levels were measured again.

The researchers found that the subjects’ thyroid profiles were impaired, consistent with other physical and psychological stress results.

Fortunately, the authors of this initial study were far-sighted enough to conduct a follow-up study two years later. The same group of women increased their training to 50 miles a week, and their thyroid function normalized; the thyroid impairment was only a transient response to the stress during a training increase.

Later research published in 2003 by L. Baylor and A. Hackney confirmed that intense training has an effect on thyroid hormone levels in female athletes, but interestingly, their study demonstrated that not all women respond the same.7 17

Female athletes underwent an intense training regimen of running, rowing and weight lifting for five months. Thyroid hormone levels remained stable in 7 of the women, while they dropped in 10 of them. This highlights the complex and poorly-understood nature of thyroid issues, particularly among women. Further research has shown that dietary factors, like iron levels and zinc intake, can also influence thyroid hormone levels.8, 9

The only thing that’s clear is that more research is needed on thyroid problems in athletes.

  • Are endurance athletes, especially females, more prone to thyroid problems than the general population?
  • Can intense training affect the balance of thyroid hormone in runners who already have hypothyroidism?
  • And do runners with thyroid problems respond to physical stresses the same way healthy runners do?

These are all questions that urgently need to be answered.

Final points

For now, the best advice from the medical community is to:

  • Find a good endocrinologist that understands your needs as a runner
  • Closely monitor your thyroid-stimulating hormone (TSH) and free thyroxine (free T4 or fT4) levels on a regular basis

Highly competitive athletes report that, while a solution may not present immediately, you should consistently take care of your body the old-fashioned way (a healthy diet and enough sleep), and modulate thyroid dosage with an endocrinologist.

Indeed, as many readers likely know, thyroid imbalance has not barred Galen Rupp from achieving a streak of consistent and healthy 10,000 m running that took him all the way to the podium at the 2012 Olympics.

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1. Bernhardt, G. Exercise and thyroid disease: part one.
2. Wiersinga, W. M., Subclinical hypothyroidism and hyperthyroidism. I. Prevalence and clinical relevance. The Netherlands Jounal of Medicine 1995, 46 (4), 194-204.
3. McDermott, M. T.; Ridgway, E. C., Subclinical hypothyroidism is mild thyroid failure and should be treated. Journal of Clinical Endocrinology & Metabolism 2001, 86 (10), 4585.
4. Villar, H. C. C. E.; Saconato, H.; Valente, O.; Átallah, A. N., Thyroid hormone replacement for subclinical hypothyroidism. Cochrane Database of Systematic Reviews 2007, (3).
5. Boyden, T.; Pamenter, R.; Rotkis, T.; Wilmore, J., Evidence for mild thyroidal impairment in women undergoing endurance training. Journal of Clinical Endocrinology & Metabolism 1982, 54 (1), 53-56.
6. Boyden, T.; Pamenter, R.; Rotkis, T.; Stanforth, P.; Wilmore, J., Thyroidal changes associated with endurance training in women. Medicine & Science in Sports & Exercise 1984, 16 (3), 243-246.
7. Baylor, L.; Hackney, A., Resting thyroid and leptin hormone changes in women following intense, prolonged exercise training. European Journal of Applied Physiology 2003, 88 (4-5), 480-484.
8. Rosenzweig, P. H.; Volpe, S. L., Effect of iron supplementation on thyroid hormone levels and resting metabolic rate in two college female athletes: a case study. International Journal of Sport Nutrition and Exercise Metabolism 2000, 10 (4), 434-443.
9. Kilic, M.; Baltaci, A.; Gunay, M.; Gökbel, H.; Okudan, N.; Cicioglu, I., The effect of exhaustion exercise on thyroid hormones and testosterone levels of elite athletes receiving oral zinc. Neuro Endocrinology Letters 2006, 1-2, 247-252.

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12 Responses on “Thyroid Imbalance in Runners: A Look at the Impact of Training on Thyroid Levels

  1. Thanks for writing about this issue. Low thyroid function is a problem that plagues me, particularly during heavy training or times of stress. I have yet to find much research on the topic. I’m looking forward to hearing the podcast and hoping to find some natural ways to keep the thyroid in balance.

  2. Have a question: are thyroid blood tests completely accurate? I heard this is not always the case. And is there another way to see if there is for example hypothyroidism? Thx

  3. Thanks for the article but what about women with hyperthyroidism? I’m a runner and terrified I can’t run anymore. I just recently became hyperthyroid. Flipped from hypo to hyper after being balanced for a year and a half. I’m waiting to see an endocrinologist. It can’t be too soon. Three years ago I gained 40 pounds over night. By the end of that week dropped 20. Lost 10 on my own but still have 10 to lose. Haven’t ran in over a year, life got in the way. Now I don’t know if I’ll ever run again. I feel awful. I’d like to know what you find about a runner with hyperthyroidism. Hypo is more common BOTH are bad but hyper is worse.

    • Hi Laura, sorry to hear about your ups and downs with your thyroid. We have not researched about this yet, but can add it to the list of topics to look into. Your endocrinologist is going to have the best information for you on this topic. Be careful though, as flips that large will put your body into a serious state of stress. Sorry we can’t help more for now.

  4. My issue is that by the end of endurance events, half and full distance ironman competitions, I end up running in either with my core collapsed forward or to the right side.

    It definitely affects my performance. I get overheated and regardless of how much I drink and eat, I can’t snap back.

    My question is, is this common to endurance athletes with hypothyroidism?

    • Hi Susan, I am sorry, I just do not have the qualifications to answer that question for you. That would be one for your physician to answer. All we have on hypothyroidism is what we shared in this post. Just be sure that you are not confusing other symptoms of running hard with this. If you are completing full iron mans, you are putting your body through a lot of stress, and everyones body will break down during that time. Most athletes are struggling towards the end of an ironman, that is what makes it so impressive to accomplish!

    • susan I have run trail runs this year after having a break from cricket I used to run ultras mainly 24 hrs, 20 yrs ago. I am finding that in a typical 20 k mountain run I overheat and drenched after first hour although i am running fairly well 6-10 kms per hr, I gradually slow down and I am suddenly exhausted and watch as everyone passes me by.
      I have been diagnosed with hashimotos previously I feel my remaining half is defunct and 50 mgs is insufficient, its hard to find a doctor interested in my sporting achievements even when i am not running a get sleepy by late afternoon and tired. but glad to read of other runners with same problem.

  5. Hi Susan, I suffer from hypothyroidism & just completed my 3rd New York Marathon. Consistent with my previous marathons, despite being well trained & super fit I ended up in the medical tent, completely de-hydrated & this is despite eating &drinking every 2 miles for the whole course. My nutrition plan was designed by a sports dietitian who specialises in endurance events .
    I was very overheated at the end of the event, my running gear was saturated & I continued to get ” night sweats ” up to 36 hours after the event.
    In addition I noticed from a video of me crossing the finish line that my body was leaning to one side very much like you describeing your core as not being able to support you.
    In short I think your theory is correct.

  6. What happened to me is quite the opposite. I was diagnosed with nodular goiter due to hypothyroidism in October 2013. My T3 was low. Then I started running in January 2014. That time I already taking my meds (Euthyrox). After 6 months, I stopped taking my meds as I always feel like my head is foggy. I can’t think clearly. I consulted my doctor right after and suggested for TH exam.

    The findings from my exam was that my T3 level increased and size of the bump/node in my neck decreased.

    After 2 years of running, I took a TH exam again and the findings are great. My T3 is normal now.

  7. I was diagnosed with hyperthyroidism about 3 months ago now and I am a freshman runner in college. I wasn’t able to finish my cross country season and i just started running again after two months after now my doctor doesn’t want me to run for a month after treatment taking the radioactive iodine. I feel like i won’t be able to run like I used to again

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