Role of Bioavailable Testosterone Confirmed in Depressed Middle-Aged Men

A reduced blood level of bioavailable testosterone may be a risk factor for depressive symptoms in middle-aged men. Results of a small study were presented at the 159^th annual Meeting of the American Psychiatric Association.

Bioavailable testosterone is the bioactive fraction of circulating total testosterone that is not tightly bound to sex hormone-binding globulin; it is thought to be more accurate than total testosterone in reflecting the clinical androgen state in men. Exogenous testosterone treatment has previously been reported to improve mood.

Researchers compared blood levels of bioavailable testosterone in 44 men (ages 40 to 65) who met criteria for a major depressive episode as part of major depressive disorder and 50 age-matched male controls without depressive symptoms.

They found that mean bioavailable testosterone and total testosterone levels were lower in the depressed men (3.51 and 11.94 nmol/L, respectively) than in controls (4.69 and 17.64 nmol/L, respectively). Futhermore, a diagnosis of major depressive disorder was a significant predictor of low bioavailable testosterone levels.

The proportion of subjects with biochemical hypogonadism—defined as a bioabailable testosterone level of 2.4 nmol/L or lower—was34% in the depressed group versus only 6% in the control group. Those rates were 61.4% and 14% respectively, when biochemical hypogonadism was defined as a total testosterone levels of less than 12.14 nmol/L.

The results indicate that untreated depressed middle-aged men may exhibit hypothalamic-pituitary-gonadal axis hypofunctioning as evinced by lower bioavailable testosterone levels.

NeuroPsych Rev August 2006