Association of Serum TSH With Handgrip Strength in Community-Dwelling Euthyroid Elderly.

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.