Association of Free Testosterone With Hypogonadal Symptoms in Men With Near-normal Total Testosterone Levels.

OBJECTIVE

To investigate the association between hypogonadal symptoms and free testosterone (FT) levels in men with near-normal total testosterone (T) levels (250-350 ng/dL) and to determine whether a discriminatory threshold for FT exists below which hypogonadal symptoms become more prevalent.

METHODS

We reviewed the charts of 3167 men who presented to an outpatient men's health clinic. Two hundred thirty-one men had symptoms of "low testosterone" and serum testosterone levels between 250 and 350 ng/dL. We evaluated hypogonadal symptoms using the Androgen Deficiency in the Adult Male (ADAM) and quantitative ADAM (qADAM) questionnaires. Serum levels of T and sex hormone-binding globulin were collected on the same day that men completed their questionnaires. We used linear regression to determine whether a threshold of FT exists for hypogonadal symptoms. We performed univariate and multivariable analyses to evaluate factors that predicted a low FT level.

RESULTS

The median age was 43.5 years, and the median testosterone and FT levels were 303 ng/dL and 6.3 ng/dL, respectively. Prevalence and severity of hypogonadal symptoms (ADAM and qADAM) were similar between men with low (<6.4 ng/mL) and normal FT levels. There was an association between age and 3 of the 10 hypogonadal symptoms (decreased enjoyment in life, sadness, and deterioration of work performance) with a low FT on a univariate analysis. Only younger age was positively associated with FT on multivariable analysis.

CONCLUSION

We did not observe a relationship between hypogonadal symptoms and FT in men with near-normal testosterone levels. Symptom-specific FT thresholds could not be defined, as age remains an important confounder.