TG and sarcopenia: found that TT3, rather than FT3, was a more stable and practical indicator to evaluate the relationship between sarcopenia and thyroid hormone in the elderly euthyroid population (20), one of the reasons for this specificity is that the subjects in their study were older than the others, most of whom were the old-old (more than 80 years-old), for FT3 is easily influenced by age, season and temperature (21, 22).