Subclinical hypothyroidism and functional mobility in older adults.
BACKGROUND
Health risks associated with subclinical hypothyroidism in older adults are unclear. Our objective was to compare the functional mobility of people aged 70 to 79 years by thyroid function categorized by thyrotropin (TSH) level as euthyroid (>or=0.4 to <4.5 mIU/L), mild subclinical hypothyroid (>or=4.5 to <7.0 mIU/L), or moderate subclinical hypothyroid (>or=7.0 to <or=20.0 mIU/L with a normal free thyroxine level) cross-sectionally and over 2 years.


METHODS
A total of 2290 community-dwelling residents participating in the year 2 clinic visit (July 1998-June 1999) of the Health, Aging, and Body Composition (Health ABC) Study, who had measured TSH level, had the capacity to walk 20 m unaided, and were not taking thyroid medication or had TSH levels consistent with hyperthyroidism or hypothyroidism. Main outcome measures included self-reported and performance-based measures of mobility (usual and rapid gait speed and endurance walking ability) assessed at study baseline (year 2) and 2 years later.


RESULTS
In age- and sex-adjusted analyses, the mild subclinical hypothyroid group (vs the euthyroid group) demonstrated better mobility (faster mean usual and rapid gait speed [1.20 vs 1.15 m/s and 1.65 vs 1.56 m/s, respectively; P < .001] and had a higher percentage of those with good cardiorespiratory fitness and reported walking ease [39.2% vs 28.0% and 44.7% vs 36.5%, respectively; P < .001]). After 2 years, persons with mild subclinical hypothyroidism experienced a similar decline as the euthyroid group but maintained their mobility advantage. Persons with moderate subclinical hypothyroidism had similar mobility and mobility decline as the euthyroid group.


CONCLUSIONS
Generally, well-functioning 70- to 79-year-old individuals with subclinical hypothyroidism do not demonstrate increased risk of mobility problems, and those with mild elevations in TSH level show a slight functional advantage.
Simonsick
Eleanor M
EM
Clinical Research Branch, National Institute on Aging, Harbor Hospital, 3001 S Hanover St, Fifth Floor, Baltimore, MD 21225, USA. simonsickel@mail.nih.gov
Newman
Anne B
AB
Ferrucci
Luigi
L
Satterfield
Suzanne
S
Harris
Tamara B
TB
Rodondi
Nicolas
N
Bauer
Douglas C
DC
D000203:Activities of Daily Living; D000367:Age Factors; D000368:Aged; D015415:Biomarkers / Q000097:blood; D015986:Confounding Factors, Epidemiologic; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000175:diagnosis*; D008297:Male; D010414:Pennsylvania; D012111:Residence Characteristics; D013714:Tennessee; D013972:Thyrotropin / Q000097:blood*; D013997:Time Factors; D016138:Walking
D015415:Biomarkers; D013972:Thyrotropin