Member Case Study: Hypothyroidism and Performance

author : AMSSM

comments : 0

How would hypothyroidism affect my racing performance and what might I expect to see next year?

Member question from KSB

In trying to solve a tingling L hand/aching L armpit problem (which may have been caused by working on a home improvement project and is being solved with PT and exercises). I was diagnosed with hypothyroidism (TSH = 24). However, I seem to have none of the symptoms in fact I just got back into triathlons this past summer and racing sprint triathlons got me into the best shape I've been in for many years. I have started taking 75 mcg/day with a re-blood test scheduled for January.

I've done a little reading about this including one article regarding hypothyroidism (HP) presenting as tendonitis (I'm grabbing at this one and hoping that it might be the cause of recurring ITB syndrome!) and I've researched HP and athletic performance and HP and migraines (would be nice if those went away as well!).

My question is as the thyroid plays a role in cell metabolism, what symptoms may I have missed that I might have seen in my racing performance and what might I expect to see next year? It took me a while to recover from racing initially which I put down to having been out of racing for a while, although my fitness and performances improved through the summer and by Sept (by my levels I was flying). I've only been on Synthroid for a few weeks so too early to see/feel any difference.
 

Answer from Trish Palmer, MD

Member AMSSM

Hypothyroidism has a large constellation of potential symptoms, with some people having no symptoms at all. Interestingly, since hypothyroidism is usually a very gradual process, some people do not realize how poorly they feel until the condition is treated and they start to feel better. Generally the thyroid is the control center of your metabolism (a very basic description). Common symptoms of thyroid problems include menstrual changes, changes in hair/skin/voice, eye changes, and constipation. Symptoms pertinent to athletes may also include fatigue, exercise intolerance, weight gain, sluggishness, heat or cold intolerance, decreased sweating, shortness of breath on exertion, slower heart rate, tendonitis, and carpal tunnel syndrome.

To answer your questions, I think it's possible that your poor recovery was likely due to the hypothyroidism, possibly in combination with the lack of training. Your improvement was likely due to the fact that exercise increases tissue sensitivity to the thyroid hormone and stimulates thyroid gland secretion, and in this way can be an important factor in the treatment of hypothyroidism.

There have not been extensive studies of athletes with hypothyroidism. A study of rats showed that hypothyroidism is associated with reduced blood flow to skeletal muscle during exercise, suggesting an impaired delivery of nutrients to, and/or removal of metabolites from skeletal muscle. This possibly contributes to the poor exercise tolerance characteristic of hypothyroidism. (McAllister RM, Delp MD, Thayer KA and Laughlin MH. Muscle blood flow during exercise in sedentary and trained hypothyroid rats. Am J Physiol Heart Circ Physiol 269: H1949-H1954, 1995.)

A study of hypothyroidic people showed a decrease in cardiac output, stroke volume, and end diastolic volume at rest, and an increase with exercise compared to when their thyroid was normalized. This suggests an alteration in cardiac performance with hypothyroidism. (Wieshammer S, Keck FS, Waitzinger J, Kohler J, AdamW, Stauch M, and Pfeiffer EF. Left ventricular function at rest and during exercise in acute hypothyroidism. Br Heart J. 1988 September; 60(3): 204–211.)

It is hard to predict how your performance may change, but you have a good shot at having even better performances as your thyroid becomes better controlled.

Trish Palmer, MD
Associate Director, Primary Care Sports Medicine Fellowship, Rush University Medical Center

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date: February 11, 2008