Is the free androgen index a useful clinical marker in male patients?

The clinical relevance of the free androgen index (FAI), a ratio of total testosterone (T) to sex-hormone binding globulin (SHBG), was investigated in a regional population of men (n = 40) and women (n = 30). The FAI correlated well with free testosterone (T) in both men (r = 0.551, p < 0.001) and women (r = 0.454, p < 0.01). However, there was considerable variability among individual patients. Moreover, the FAI showed no association with sperm parameters in male patients, although total T and free T showed weak associations. The FAI may be a cost-effective alternative to free T measurement in the diagnosis of oligomenorrhea and hirsutism in women as previously shown, but may have little relevance in men.