Can you fool the test? Can someone simply overtrain and make it appear like there is a thyroid problem?
The answer is maybe and no.
Maybe, if a doctor doesn’t actually diagnose you and instead relies solely on a TSH number. If a doctor does that then manipulations of training, stress, taking certain medications, etc. can all alter TSH.
If the doctor is competent at all and goes through a full diagnosis, it’s much harder to create a “false” hypothyroid. The problem though goes back to what is hypothyroid, since endocrinologists can’t quite define it.
Focusing first on TSH, if we look at the research TSH changes acutely immediately after hard workouts. So if you went and did a hard workout then an hour later went and got your blood drawn, you’d see changes in TSH levels most likely. It’s not surprising. You just stressed your body and it needs time to come down to normal. A relatively short time after the workout a normal persons TSH levels are normalized. Even with a very hard workout, the swing isn’t terribly large.
In a study by Schmid et al. (1982 TSH, T3, rT3, and fT4 in maximal and submaximal physical exercise) they found that after maximal exercise in runners, TSH actually dropped before starting to return to normal. During submaximal, there was a gradual increase from 1.35 to around 1.5 at the end of exercise. So a subtle shift. Similarly, a 1971 study by Terjung found no changes in TSh, 30min, 3hrs, and 24hrs after 30min at 61%VO2max. Similarly (Dessypris et al. 1980) found no change in TSH after a marathon. A more recent(Ciloglu et al. 2005) study found that during exercise TSH levels changed from 1.69 at 45%, 1.78 at 70%, and 1.89 at 90% HR max. So again, exercise changes things acutely, but not a ton.
On the other hand, certain types of exercise has actually been shown to decrease TSH temporarily!
Given that, I would recommend getting blood work on an easy day, not following a hard workout.
What about over the long haul? It’s hard to study over months and months, but here’s the best the research gives us.
1. One study tracked TSH changes in 16 professional cyclists during the Vuelta a Espana in 1998 (which maybe means these dudes were on EPO?...) Anyways. Over the 3 week T4, free T3, and free T4 changed, which is what you’d expect, but there was no change in either TSH or free T3. Hoyos et al. (2001)
http://www.karger.com/Article/FullText/48112
2. Barron et al. 1995 – Took 6 marathon runners and followed them for 4 months until 2 showed signs of overtraining which was defined as having all physical symptoms (heavy legs, fatigue, etc.), mental symptoms (apathy), and decrease in performance that lasted at least 3 weeks. In these athletes, no change in TSH occurred. (Hypothalamic dysfunction in overtrained athletes)
3. Lehman et al.1999, 1993 performed a series of studies where they tried to over train 8 runners. They took one group and increased their volume for 5 weeks, and another and increased their intensity for 4 weeks. In the volume study they went from their normal average of 86km/wk to 177km/wk. In the intensity study, they increased interval volume from 9km/wk to 23km/wk. What they found was no change in TSH whatsoever.
4. In recreational athletes, they took them and had them do 4 “units” per week of high intensity endurance running (90% of threshold) and 2 units of interval workouts (3-5x3-5min segments at 110% of 4mmol level) on a bike for 6 weeks. They then checked hormone levels and found that there were no significant changes in TSH, among other hormones (Gastmann et al. 1993)
Does this mean TSH does not change over the long term or due to overtraining? No, but it does mean that it’s more difficult than just go train hard and have your TSH change.
The reason I mention this is because there’s this concept that if you just go train hard you can make your thyroid appear hypothyroid. We will touch on this a bit more later.
But, with TSH levels, there is a big distinction to make. If you killed yourself in training and did manage to elevate TSH, with time off it would normalize if you have no problem. If you have a legit hypothyroid issue, if you took 3 months off, your TSH would still be elevated. If you have a legit problem, no amount of rest/time off will normalize things.
But for sake of thoroughness, a ton of things can alter TSH. Just perusing through the research, here’s a few:
Can potentially depress TSH:
Birth control, glucocorticoids, aspirin, anti-depressants, depression itself, pregnancy, aging, fasting, exercise
Can potentially increase TSH:
Stress, emotional arousal, cold exposure, sleep deprivation, severe illness, iodine, lithium, and high high doses of anti-histamines.