Sex hormone binding globulin is associated with androgen deficiency features independently of total testosterone

Summary

Objective

It is recognized that total testosterone (TT) does not sufficiently describe androgen status when sex hormone binding globulin (SHBG) is altered. However, in humans, evidence supporting the existence of a hypogonadism due to low T bioactivity is scanty. The aim of the study was to assess whether changes in SHBG levels, independently of TT, are associated with subjective and objective androgen dependent parameters.

Design

Cross-sectional observation.

Patients

2622 men (aged 51.1±13.5 years) attending a Sexual Medicine and Andrology Outpatient Clinic for sexual dysfunctions.

Measurements

All patients underwent a standardized diagnostic protocol before starting any treatment. Clinical and biochemical parameters have been collected. Higher ANDROTEST score has been used as a comprehensive marker of more severe hypogonadal symptoms. Prostate specific antigen (PSA) and hematocrit have been used as objective surrogate markers of T bioactivity.

Results

After adjusting for TT and lifestyle, SHBG showed a significant positive association with ANDROTEST score (B=0.79 [0.61;0.96], p<0.0001). Conversely, higher SHBG, independently of TT, was negatively related to PSA (B=-0.86 [-0.83;-0.89]; p<0.0001) and hematocrit (B=-0.64 [-0.88;-0.40]; p<0.0001), after adjustment for the aforementioned confounders along with age and body mass index. Furthermore, a relationship between SHBG and lipids or blood pressure was found, with lower SHBG levels associated with a worse metabolic profile, independently of TT.

Conclusions

Higher SHBG, independently of TT, is associated with either subjective or objective androgen deficiency features. This indicates that besides a hypogonadism due to an impaired T production, a hypogonadism due to a lower biological activity of T does exist.

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