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Published on: July 5, 2017
Compared to total serum testosterone, calculated free testosterone has a stronger association with lean mass, muscle
Kristian Villars Lolck1,2, Julian Alcazar3,4,5, Rikke Stefan Kamper3,6
1Department of Geriatric and Palliative Medicine, Copenhagen University Hospital, Bispebjerg and Frederiksberg, Copenhagen, Denmark. kristian.kaltoft.lolck@regionh.dk.
Background:
Low serum testosterone concentrations have been associated with low muscle mass and strength in older men. However, the existing literature is inconclusive.
Aim:
To investigate the differences in the relationship between total and calculated free serum testosterone and muscle status, in young vs. old men.
Methods:
Body mass index (BMI), fat percentage, appendicular lean mass (ALM), percentage ALM (ALM%), skeletal muscle index (SMI), handgrip strength (HGS), leg extension power (LEP) and 30-s sit-to-stand performance (30-s STS) were measured in 557 healthy Danish men (326 younger (≤ 65 years) and 231 older (> 65 years)) aged 23-92 years. Total serum testosterone, sex hormone binding globulin and albumin were measured (ELISA) and subsequently, calculated free testosterone and free testosterone index (FTI) were computed. A general linear model examined the relationship between testosterone and individual muscle parameters, with age group-interaction, while a pooled effect model examined the relationship between testosterone and a compound of all muscle parameters, adjusted for age, BMI and fat percentage.
Results:
Total testosterone was negatively associated with 30-s STS in younger men, and positively associated with LEP in older men. Calculated free testosterone was positively associated with LEP in younger and older men, as well as SMI, ALM%, HGS and 30-s STS in older men. Calculated Free testosterone and FTI, but not total testosterone, were positively associated with the muscle compound in older men.
Conclusion:
The present data indicates that calculated free testosterone, compared to total testosterone, is more closely linked to muscle status and physical performance in older men.
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