Association of thyroid function with sarcopenia in elderly Chinese euthyroid subjects

Area of Science:

• Endocrinology
• Gerontology
• Muscle Physiology

Background:

• Sarcopenia incidence rises with the aging population globally.
• Thyroid hormones significantly influence body composition and physical function.
• The relationship between thyroid hormone levels and sarcopenia in elderly euthyroid individuals is not fully understood.

Purpose of the Study:

• To investigate the impact of thyroid hormone concentrations on muscle mass, strength, and physical function in elderly Chinese euthyroid subjects.
• To explore the association between free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) levels and sarcopenia indicators.

Main Methods:

• Study included 94 elderly Chinese euthyroid subjects.
• Measured FT3, FT4, and TSH levels using immunoassays.
• Assessed appendicular skeletal muscle mass (ASM) via dual-energy X-ray absorptiometry, handgrip strength, and physical function (Short Physical Performance Battery - SPPB).

Main Results:

• FT3 showed positive associations with ASM, handgrip strength, and SPPB.
• Muscle function (handgrip strength, SPPB) was negatively associated with age, and FT3 demonstrated age-dependent decline.
• No significant associations were found between FT4 or TSH and sarcopenia parameters; subjects with sarcopenia had lower FT3 levels.

Conclusions:

• Higher FT3 concentrations within the normal range are linked to greater muscle mass and improved muscle function in elderly individuals.
• FT3, but not FT4 or TSH, is a significant factor associated with sarcopenia in euthyroid elderly subjects.