Association of Serum TSH With Handgrip Strength in Community-Dwelling Euthyroid Elderly
Beom-Jun Kim1, Seung Hun Lee1, Carlos M Isales2
1Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
Context:
Despite apparent muscle weakness in overt or even subclinical hyperthyroidism, the effects of thyroid function in the reference range on muscle strength are unknown.
Objective:
To investigate the association of serum TSH and free T4 with handgrip strength (HGS) in euthyroid elderly.
Design And Setting:
A nationally representative population-based, cross-sectional study from the Korea National Health and Nutrition Examination Surveys.
Participants:
A total of 650 men aged ≥50 years and 533 postmenopausal women.
Main Outcome Measures:
HGS was measured using a digital grip strength dynamometer, and low muscle strength was defined based on the Korean specific cutoff point of HGS (28.9 and 16.8 kg in men and women, respectively).
Results:
After adjustment for confounders, lower serum TSH but not free T4 was associated with lower HGS in men (P = 0.032). Compared with men with high-normal TSH, those with low-normal TSH consistently showed 5.0% lower HGS (P = 0.027), with a linear decrease in HGS across decreasing serum TSH quartiles (P for trend = 0.018). Men with low muscle strength had 22.0% lower serum TSH than those without (P = 0.015), and the odds for the risk of low muscle strength was 3.76 times higher among men with low-normal TSH than it was among those with high-normal TSH (P = 0.021). However, these associations were not observed in postmenopausal women.
Conclusions:
These results suggest that serum TSH level at the lower end of reference range may be associated with low muscle strength, especially in older men.
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