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

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: Two thousand six hundred and twenty-two 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 haematocrit 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 < .0001). Conversely, higher SHBG, independently of TT, was negatively related to PSA (B = -0.86 [-0.83; -0.89]; P < .0001) and haematocrit (B = -0.64 [-0.88; -0.40]; P < .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.