CONTEXT: Physiological changes in thyroid hormone concentrations might be 
related to changes in the overall physical function in the elderly.
OBJECTIVE: We determined to what extent thyroid hormone concentrations are 
related to physical function and mortality in elderly men.
DESIGN: A longitudinal population study (the Zoetermeer study) was conducted. 
Mortality was registered in the subsequent 4 yr.
PARTICIPANTS: Four hundred three independently and ambulatory living men (aged 
73-94 yr) participated.
MAIN OUTCOME MEASURES: The study examined the association between serum thyroid 
hormones and parameters of physical function as well as the association with 
mortality.
METHODS: TSH, free T4 (FT4) total T4, T3, rT3, and T4-binding globulin were 
measured. Physical function was estimated by the number of problems in 
activities of daily living, a measure of physical performance score (PPS), leg 
extensor strength and grip strength, bone density, and body composition.
RESULTS: Serum rT3 increased significantly with age and the presence of disease. 
Sixty-three men met the biochemical criteria for the low T3 syndrome (decreased 
serum T3 and increased serum rT3). This was associated with a lower PPS, 
independent of disease. Furthermore, higher serum FT4 (within the normal range 
of healthy adults) and rT3 (above the normal range of healthy adults) were 
related with a lower grip strength and PPS, independent of age and disease. 
Isolated low T3 was associated with a better PPS and a higher lean body mass. 
Low FT4 was related to a decreased risk of 4-yr mortality.
CONCLUSIONS: In a population of independently living elderly men, higher FT4 and 
rT3 concentrations are associated with a lower physical function. High serum rT3 
may result from a decreased peripheral metabolism of thyroid hormones due to the 
aging process itself and/or disease and may reflect a catabolic state. Low serum 
FT4 is associated with a better 4-yr survival; this may reflect an adaptive 
mechanism to prevent excessive catabolism.