Body composition, but not morphological masculinity, is associated with biological aging markers in middle-aged men.

According to the limited soma hypothesis, androgens drive the development of male reproductive traits, including morphological masculinization, but may also impose costs on somatic maintenance and accelerate biological aging. However, the relationship between androgens and biological age remains unclear, with evidence suggesting rather beneficial effects of testosterone in aging men. The study included 176 healthy men (Mage = 53.8 ± 2.99 years). Biological age was assessed using high-sensitivity C-reactive protein, interleukin-6, tumor necrosis factor-α, soluble α-klotho, growth hormone, insulin-like growth factor-1, dehydroepiandrosterone, dehydroepiandrosterone sulfate, follicle-stimulating hormone, and luteinizing hormone. Morphological masculinity was evaluated using sexually dimorphic traits dependent on androgen levels (facial width-to-height ratio, shoulder-to-hip ratio, waist-to-hip ratio, fat-free mass, second-to-fourth digit ratio, handgrip strength, and torso strength). Analyses controlled for socioeconomic status, lifestyle, body adiposity, height, and cortisol levels. In unadjusted analyses, greater fat-free mass was associated with lower inflammatory marker levels and higher growth hormone concentrations, whereas a higher waist-to-chest ratio was associated with higher inflammation. However, these associations disappeared after adjustment for adiposity. The findings do not support the hypothesis that greater morphological masculinization reflecting higher androgen exposure is associated with accelerated biological aging. Instead, body composition and adiposity appear to play a more prominent role. The relationship between testosterone and biological age remains complex and may reflect both beneficial and context-dependent effects.