Physical Performance in Elderly Outpatients with Subclinical Hypothyroidism Compared with Euthyroid Counterparts

Background: There continues to be controversy on the clinical relevance of elderly mild subclinical hypothyroidism (SH), defined as a TSH elevation (4.0-9.99 µIU/L) with normal free thyroxin levels. Objective: To compare physical performance (PP) in elderly individuals with a TSH level above normal range versus normal counterparts. Design: Case-control study of ambulatory patients enrolled between January 2009 and December 2010. Setting: Outpatient geriatric service. Participants: Elderly individuals 65-84 years old (y/o) with SH and without conditions known to affect physical mobility. Measurements: The Short Physical Performance Battery (SPPB) was performed. The statistical analysis used the Mantel-Haenszel odds ratio (M-H-OR) method and Student’s t test with an alpha of 0.05. Results: Of the 183 individuals screened, 28 (15.3%) had SH. The study response was 89.3%, thus 25 individuals with SH were compared to 27 euthyroid controls matched by age and sex. Gender and age influence SPPB, increased age was associated with <4 points balance: 13.8% in 65-74 y/o vs. 44.0% in 75-84 y/o, χ2=6.1, p<0.05; strength of dominant leg and SPPB score were higher in men than women (both, p<0.05). Body mass index was higher in SH than controls in men (29.3 ± 2 vs. 23.4 ± 3, t=3.2, <0.02). Women with SH had a worse SPPB score than the control group, M-H-OR=8.4, p<0.05. Confidence intervals of mean gait speed were 0.73-0.95 vs. 0.98-1.14 m/s, respectively with results in men lacking significance. Chair stands were longer in SH than controls: 13.5 ± 2.4 vs. 10.0 ± 1.7 seconds for men and 20.6 ± 12.6 vs. 14.8 ± 2.9 seconds for women, both p<0.05. Conclusions: These data suggests an association between SH and lower physcial performance. This warrants further study to define if T4 supplementation improves physcial performance, thus preventing frailty.