Aims: Type 2 diabetes (T2D) is associated with lower testosterone (T) concentrations in men and higher concentrations in women, decreases in sex hormone-binding globulin (SHBG), aerobic fitness and muscle strength. Whether this association is mediated by obesity, hyperglycaemia or sex remains unclear. We tested the hypothesis that T concentrations will be lower in men and higher in women with T2D, while SHBG concentrations will be lower in both sexes with T2D compared to those who are non-obese or obese without T2D. We hypothesised that such sex hormone concentrations changes will be associated to lower physical function, glucose control, and muscle mass independent of sex.
Methods: Sixty-seven adults (45 men / 22 women, 46-57 years) were categorised in to three groups non-obese (n=20), obese (n=21), T2D (n=26). Blood sampling (sex hormones and markers of glucose control), aerobic fitness (VO2peak), muscle strength (1 repetition maximum), and body composition (dual energy x-ray absorptiometry) was assessed. Data were analysed using linear regressions and univariable analysis.
Results: Men with T2D had lower T and free testosterone (fT) compared to their non-obese or obese counterparts (p <0.05) but had no differences in SHBG (p >0.05). Women with T2D had no differences in T or fT but had lower SHBG compared to non-obese individuals (p <0.05). In men, lower T and fT was associated with lower VO2peak and lean mass (p <0.05), while lower SHBG was associated with poorer glucose control and leg strength (p <0.05). In women, lower T and SHBG was associated with poorer glucose control and lower lean body mass (p <0.05)
Conclusion: Regardless of sex, lower circulating concentrations of sex hormones is related to poorer functional capacity, glucose control and lower lean mass. Restoration of sex hormones concentrations should be prioritised by clinicians for both sexes to improve glucose control and functional outcomes.