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.
Sheba Medical Center, Leviev Heart Institute, 52621 ISRAEL, Tel-Hashomer, Israel, 52621, 03-7160634 ; email@example.com.
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.
Top two moths are Heart Moth from The Moths of the British Isles Second Series/Chapter 2.