madman
Super Moderator
Introduction
The association between circulating testosterone (T) levels and male sexual function was found to be stronger for free T than for total T. However, most studies have relied on calculated free T rather than directly measured free T (mFT).
Objective:
To investigate the association between mFT and sexual function in community-dwelling men.
Methods
The European Male Ageing Study assessed sexual function (frequency of sexual thoughts, sexual intercourse, petting, morning erection and orgasm, erectile (dys)function and sexual desire) using a validated questionnaire. mFT was measured by liquid chromatography–tandem mass spectrometry following equilibrium dialysis in an EMAS subset (n = 526). Proportional ordinal logistic regression and restricted cubic spline regression, adjusted for age, BMI and study center, were used to investigate sexual function outcomes in relation to mFT.
Results
The mean age in this EMAS subset was 70.5 ± 8.5 years, with a mean body mass index of 27.3 ± 3.3 kg/m² and mean mFT of 198 ± 82 pmol/L. In proportional ordinal logistic regression models, lower mFT was significantly associated with erectile dysfunction (odds ratio (OR) per 10 pmol/L decrease 1.04 [95% confidence interval (CI) 1.01 - 1.06], p < 0.01), fewer sexual intercourse (OR 1.03 [1.00 - 1.06], p < 0.05), lower frequency of orgasm (OR 1.03 [1.01 - 1.06], p < 0.05) and reduced sexual desire (OR 1.03 [1.01 - 1.05], p < 0.05). Consecutive restricted cubic spline models suggested a nonlinear association between mFT and both erectile function and orgasm frequency. The risk of erectile dysfunction increased with a decrease in mFT: values below a threshold of 163 pmol/L were associated with a markedly steeper increase in the predicted probability of worse erectile function. Similarly, mFT values below 138 pmol/L were associated with a sharp increase in the predicted probability of decreased orgasm frequency.
Conclusion
In community-dwelling men, lower mFT was associated with worse erectile function, fewer attempts at sexual intercourse, reduced orgasm frequency, and lower sexual desire, with evidence of non-linear thresholds for erectile dysfunction and orgasm frequency at 163 and 138 pmol/L, respectively.
