On Synthroid and Elite Athletes

Recently, an article was published in the Wall Street journal that has really got me thinking.

The article profiles “US Track’s Unconventional Physician,” an endocrinologist by trade who has treated several high profile athletes for “subclinical hypothyroidism.” To summarize the article, typical TSH (thyroid stimulating hormone) cut-offs are around 5, depending on your laboratory, and, I presume, depending on the signs and symptoms of the patient. Dr. Brown, the physician profiled, considers his threshold to be 2, meaning that, to him, a TSH of 2 combined with symptoms means an underactive thyroid. He has been prescribing synthroid (thyroid hormone replacement) for some athletes he has diagnosed with hypothyroidism…with good results…15 Olympic gold medals and counting.

By sub-clinical, the medical establishment means that the patient’s free T4 (thyroid hormone itself) is normal, while the TSH is elevated or slightly elevated.   To my best understanding, this is a somewhat newer disease entity that has not been as well characterized or protocolized in treatment schemes. In addition, one could argue that a sub-clinical case is actually a future overt hypothyroid patient waiting to be found and supplementation should be started to prevent any adverse effects of the disease. However, as a caveat, I am just a medical student and not a board certified endocrinologist or even a doctor (yet), so, I would take what I write here with a grain of salt (and I’m also writing this a fairly quickly, no time for editing!).

Now, to be clear, I am not an endocrinologist nor am I a professional athlete, so I really have no dog in this fight. But, I did read the article with a keen interest as “curious observer.”

Here are the questions that popped into my head as I read:

1. What is the mechanism of this disease? 

The most common cause of hypothyroidism in the US is Hashimoto’s thyroiditis, an autoimmune disease in which you have autoantibodies against certain proteins in the thyroid gland (for example, thyroid peroxidase). However, seeing as autoimmunity was not mentioned in the article, my best guess would be that hard training suppresses the hypothalamus, which is upstream in the chain of events in stimulating the thyroid gland (hypothalmus secretes TRH–> pituitary  secretes TSH –> thyroid secretes thyroid hormone), somewhat like how anorexia can cause you to stop having a period (hypothalmic suppression then suppresses the menstrual cycle).

2. Is this effect reversible when the person stops training if he is claiming that it is the hard training that is suppressing the thyroid?

Or, stated another way, is this a temporary under-active thyroid? Or have they permanently lost thyroid function?

IF my proposed mechanism is what Dr. Brown or others was thinking, then is this effect reversible when not in a hard training mode and did has anyone retest TSH at that time to see? [If anyone has any papers on this, please send along! Not enough time for a thorough literature search tonight…]

3. Do the athletes stay on synthroid (thyroid hormone replacement) after they are done competing?

Excess thyroid hormone isn’t without consequence! Unless you like heart arrhythmias (atrial fibrillation in this case) and accelerated bone loss…

4. Has anyone suggested that this is due to some sort of immunosuppressive process and, if so, is it somehow linked to the seemingly increased rates of gluten intolerance in elite runners?

I actually have no data to back up that gluten intolerance claim it just seems that nearly every elite runner that I’ve met (which is like, what, 5?! really making a claim on nothing here) is intolerant to gluten.

Just an interesting thought to me…is there something about hard training that abnormally affects physiology to make these people susceptible to depressed thyroid function and gluten intolerance? However, these might be “true, true, unrelated” – both entities found in elite athletes, but in no way related in how they come about.

5. Does this constitute a new performance enhancing drug?

And, here’s an ethical issue I’m not sure I want to add my opinion to, seeing as I’m not a professional endocrinologist nor athlete and really have no place giving an opinion.

Surely, if you need replacement therapy (if you have Hashimoto’s, if you had your thyroid gland surgically removed) it isn’t “performance enhancing” as you do need thyroid hormone to live.

However, is adding replacement to someone who may not necessarily be hypothyroid, but is tired and has a borderline TSH constitute using a performance enhancing drug? I’m not really willing to say without knowing more information. Also, who isn’t tired? Were these athletes having more symptoms other than fatigue?

It’s just an interesting idea to ponder.

6. If Dr. Brown is right, are we missing an entire population who needs hormone replacement? Should you replace hormone in, say, a 35 year old male with a TSH of 3.5 who is a little tired, but isn’t an elite athlete?

Anyways, speaking of tired, I need to settle down the brain, read some on gynecology, and go to bed.


Until next time…