Differences in Heart Rate Profile during Exercise among Subjects with Subclinical Thyroid Disease

[helvella]

This paper highlights the fact the subclinical thyroid disease causes significantly different responses to exercise. Both hypothyroidism and hyperthyroidism.

It does make me wonder what the results would be if everyone were given this sort of exercise-response test (as well as blood tests)? Might provide a clear indication even when the TSH level is unexceptional.

Thyroid. 2013 Jun 18. [Epub ahead of print]

Differences in Heart Rate Profile during Exercise among Subjects with Subclinical Thyroid Disease.

Maor E, Kivity S, Kopel E, Segev S, Sidi Y, Goldenberg I, Olchovsky D.

Source

Sheba Medical Center, Leviev Heart Institute, 52621 ISRAEL, Tel-Hashomer, Israel, 52621, 03-7160634 ; [e-mail].

Abstract

Background: Clinical thyroid disease is associated with changes in the cardiovascular system, including changes in heart rate during exercise. However, data on the relation between subclinical thyroid disease (SCTD) and heart rate during exercise are limited.

Methods: We investigated 3,799 apparently healthy subjects who were evaluated in the Institute for Preventive Medicine at the Sheba Medical Center. All subjects answered standard health questionnaires, were examined by a physician, completed routine blood tests including TSH, free T3 and free T4 levels, and underwent a treadmill exercise according to the Bruce protocol. Subjects with known thyroid disease or those who were taking thyroid related drugs were excluded from the analysis. Heart rate profile was compared between patients with subclinical hypothyroidism (SCHypoT), normal thyroid functions and patients with subclinical hyperthyroidism (SCHyperT) using propensity score matching.

Results: Seventy patients had SCHyperT and 273 had SCHypoT. Compared with age and gender matched normal subjects, SCHyperT subjects had higher resting heart rate (83±17 vs. 76±12 beats per minute [bpm], p=0.006), significantly higher recovery heart rate (94±12 vs. 90±12 bpm, P=0.045) and a significantly lower heart rate reserve (80±20 vs. 87±18 bpm, P=0.006). Subjects with SCHypoT showed a trend toward a lower resting heart rate (75±13 vs. 77±15 bpm, P=0.09) and had a significantly lower recovery heart rate (88±12 vs. 90±13 bpm, P=0.035). There was no significant difference in exercise duration between subjects with SCTD and their matched normal controls.

Conclusions: Subjects with subclinical thyroid disease have significantly different heart rate profile during rest, exercise and recovery.

PMID:

23777550

ncbi.nlm.nih.gov/pubmed/237...

Rod

Top two moths are Heart Moth from The Moths of the British Isles Second Series/Chapter 2.

[Hidden]

I find this sort of paper and research really interesting. It makes a lot of sense that thyroid issues would show distinct patterns in heart rate profiles.

Having done this heart rate profile with the treadmill exercise myself, I know that when undiagnosed and untreated, it would have been impossible for me to complete. Unfortunately I suspect that many with undiagnosed/untreated thyroid issues would not be able to use the treadmill in the first place.

Thanks for posting.

Beautiful picture!

Liza

[lynx]

I think this was a very good experiment, demonstrating what a layman might expect. I am surprised it hadn't been thought of before.

A flip side to this would be those taking insufficient ndt, t4, and t3 taking the same test. I think they might come out even worse in this experiment. I think it is because when the thyroid is untreated the body just about copes with demands. If slightly treated the body seems to be just confused and powers down.

Having a bit of a foggy off day sorry I cant find the words..

[helvella Administrator in reply to lynx]

There have been some vaguely similar experiences before. It is certainly well-documented that hypo and hyper, even when sub-clinical, have their impacts on exercise/heart. Simply does not appear to have moved from research papers into doctor's brains!

I think your point about re-doing after treatment and, specifically, while on incorrect treatment, is a very good point. There does seem to be a vast pool of inappropriately treated people to use in such trials/tests!

I am emailing the paper's authors with your point - it seems so valid and sensible.

Rod

[spiral]

i know i would not be able be able to do this treadmill test in any way. i have been told by my gp i have normal thyroid test results despite having a lot of the symptoms of hypothyroidism. if this treadmill test somehow helps with diagnosis it has to be a good thing. Personally i would do anything right now to get a good doctor and a diagnosis

[super1]

Can someone explain the results in simple English.

[helvella Administrator in reply to super1]

If your thyroid hormone levels are wrong - whether too high or too low - but not treated (because it is sub-clinical), your heart behaves differently to healthy people.

These differences appear to be characteristic of your thyroid hormone levels.

This applies when you are at rest, when you are doing exercise, and when you are recovering after exercise.

Rod

[super1]

Thanks Rod, I understood that much but just wanted a explanation of what the results meant

such as 83±17 ?

Seventy patients had SCHyperT and 273 had SCHypoT. Compared with age and gender matched normal subjects, SCHyperT subjects had higher resting heart rate (83±17 vs. 76±12 beats per minute [bpm], p=0.006), significantly higher recovery heart rate (94±12 vs. 90±12 bpm, P=0.045) and a significantly lower heart rate reserve (80±20 vs. 87±18 bpm, P=0.006). Subjects with SCHypoT showed a trend toward a lower resting heart rate (75±13 vs. 77±15 bpm, P=0.09) and had a significantly lower recovery heart rate (88±12 vs. 90±13 bpm, P=0.035). There was no significant difference in exercise duration between subjects with SCTD and their matched normal controls.

[helvella Administrator in reply to super1]

That is saying that the median of resting rate for SCHyperT was 83 within a range of plus or minus 17. So, bottom value 66, median 83, top value 100. Whereas the healthy group had a bottom value 64, median 76, top value 88. It is trying to give some idea of how the values were spread in the group being tested.

It would be necessary to look at the full article to be certain of what they measured and how.

The p values are trying to give some idea of the difference (say, between 83 and 76) being due to chance alone and having no significance. Have a look here:

en.wikipedia.org/wiki/P_value

Rod

[super1]

thanks, good explaination

[GRConwy]

I used to do a lot of competitive cycling when I was undiagnosed, my HR then used to be in the 40's & low 50's bpm, high 20's / low 30's on waking! I could win races on flat courses, but rubbish in the hills. Only the occasional leisure ride now, but with T3, iron, multivits etc I seem to effortlessly cruise up any incline. If only I could turn the clock back.

[Hidden]

I am having regular blood tests every 6 weeks along with other investigations and all testing should be complete 29 August when I should be given full diagnosis. I was told by my endocrinologist under no circumstances undertake any exercise during this period or it will mislead the results.

[snowflake]

Chickens12, this interests me as I am convinced that my thyroid effects the intensive exercise I do (or visa versa) I have always wondered if I needed more or less thyroxin depending on exercise and how it effects my metabolism. The only way I guess would be to test like a diabetic during the day but I think the Thyroxine in the blood may not be read like that? anyway, if you have been told not to do exercise, it must have some sort of effect on results.

[Whippetlover]

This is interesting and I would love to have this test done. I have had very odd heart rates on gym exercise machines. It's very high during exercise and takes a long time to settle down. (I'm hypo on T3 and T4 but much lower than I was on).

I had surgery last year and was kept in for an extra day due to concerns over my heart rate. They suspected a heart attack but this was then ruled out. No explanation has every been offered. I'd be very interested to know if anybody else has had similar experiences.