Bioavailable Testosterone Should be Used for the Determination of Androgen Levels in Infertile Men

Abstract

We determined the relationship between total testosterone and bioavailable testosterone in men presenting with infertility. In addition, the effects of body mass index and age on testosterone levels were examined. To determine if total testosterone measurements are an accurate reflection of tissue available testosterone in infertile men, levels of total testosterone were compared to bioavailable testosterone levels. Males presenting with infertility were studied. A total of 73 patients underwent complete history and physical examination. Serum levels of total testosterone and bioavailable testosterone were measured as a morning sample in all patients. Patients were classified as having low, normal or high levels of total or bioavailable testosterone. To determine the effect of obesity, patient weight was converted to body mass index for analysis. Of 73 patients evaluated 34 (47%) had low total testosterone levels while only 19 (26%) had low bioavailable testosterone levels. The discrepancy between total testosterone and bioavailable testosterone was even greater in men older than 40 years with 10 of 17 (59%) having low total testosterone levels and 8 (80%) having normal bioavailable testosterone levels. Body mass index negatively correlated with total testosterone and bioavailable testosterone levels. Testosterone status should be determined by the measurement of bioavailable testosterone when evaluating infertile males.