Poster Presentation ESA-SRB-ANZOS 2025 in conjunction with ENSA

Men borderline low serum total testosterone concentration and low sexual desire – does the calculation of free testosterone add value? (127178)

Gary Wittert 1 2 3 , Andrew Vincent 2 3 , Mahesh Umapathysivam 3 4 , David Jesudason 1 3 , Sam Tafari 1 3 , Wen Huey Goai 1 3
  1. Endocrine and Metabolic Unit, Royal Adelaide Hospital, Adelaide, SA, Australia
  2. Freemasons Centre for Male Health and Wellbeing, South Australian Health and Medical Research Institute, Adelaide, SA, Australia
  3. University of Adelaide, Adelaide, SA, Australia
  4. Endocrine Unit, Flinders Medical Centre, Adelaide, SA, Australia

Background:
Guidelines recommend diagnosing androgen deficiency by symptoms e.g. sexual desire plus low serum total testosterone (TT). Studies vary as to whether calculated free testosterone (cFT) adds diagnostic accuracy when TT is borderline low.

Aim:
To determine whether, in men with borderline low TT, cFT improves the ability to infer that insufficient testosterone exposure is related to low sexual desire (SD).

Methods:
A cross-sectional analysis was conducted in 1,195 community-dwelling men aged ≥35 years. TT (via LCMS), cFT (Vermeulen equation), and sexual desire using the Sexual Desire Inventory (SDI) were assessed. Men were classified as having borderline low TT if 6.1-12 nmol/L, low cFT if <0.20 pmol/L and low SDI if <19. Data were analysed by linear regression, with and without age and fat mass adjustment. Exact binomial confidence intervals for the diagnostic accuracy measures were generated.

Results:
Among the 1,169 men with complete data, the mean age was 55 years and BMI 28.6 kg/m². 12 had low TT and 207 had borderline low TT. Men with TT<12 were older (p=0.02), more obese (p<0.001), and had lower SDI scores (p<0.001). In men with borderline TT, a linear association between sexual desire and cFT was explained by age and fat mass. Prevalence of low sexual desire was 23.3% in men with borderline low TT. In men with a low cFT (<0.2), this was 41.9% compared to 18.3% in men with normal/high cFT (positive predictive value 41.9%, negative predictive value 81.7%, false positive 58.1%, and false negative 18.3%).

Conclusion:
In men with borderline low TT, low cFT is weakly predictive of low sexual desire; the effect is better explained by age. Normal cFT is of greater value to exclude low sexual desire in younger but not older men with borderline low TT.