Methods

Data were collected from community-dwelling 957 middle-aged and elderly men. 

Leg and arm (appendicular) muscle mass muscle mass) was measured with dual-energy X-ray absorptiometry (DHEXA) at baseline and 10 year follow-up examinations. 

Total testosterone (TT) and free testosterone (FT) were measured with a radioimmunoassay. 

The calculated FT (cFT) was determined with Vermeulen's formula, based on total testosterone, albumin, and sex hormone-binding globulin (SHBG) levels. 

Results

After adjusting for baseline age, leisure-time physical activity, nutrition intake (total energy, total protein, vitamin D), medical history (stroke, heart disease, cancer, diabetes, osteoporosis, rheumatoid arthritis), and smoking habit at baseline, no association was found for total testosterone levels and muscle mass loss. 

However, there was a significant association of free testosterone levels (both measured and calculated) with loss of muscle mass. 

Men with the lowest free testosterone levels (calculated), below 46.3 pg/ml, had approximately a 2.1- to 2.7-fold risk of significant muscle loss compared to those with level above 46.3 pg/ml). 

Men with the lowest measured free testosterone levels, below 7.7 pg/ml, had approximately a 1.8- to 2.9-fold risk of significant muscle loss compared to those with level above 46.3 pg/ml). 

Conclusion

This study shows that middle-age and older men with low free testosterone levels are at 2-3 fold greater risk of losing a significant amount of muscle. It is notable that this significant association between low free testosterone levels (regardless of whether free testosterone was calculated or measured) and muscle loss remained after adjusting for age, medical history, nutrition intake and physical activity. 

Thus, this study shows that low free testosterone levels are independently associated with muscle loss in middle-aged and elderly men, and may be an indicator of future muscle loss. Therefore, increasing free testosterone levels with appropriate therapies, such as TRT (testosterone replacement therapy) and/or fat loss, may reduce the risk of muscle loss during ageing and prevent the onset of sarcopenia and frailty. 

 

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