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In evaluating men with suspected hypogonadism, some clinicians start by ordering total testosterone (T) levels; others order free or bioavailable T levels, which presumably identify biochemical hypogonadism more accurately. Many factors (including obesity, drugs, comorbidities, assay variability, and time of day) affect total T levels.
In this study, Veterans Administration researchers analyzed data from 3700 men (mean age, 60; nearly half obese) in whom evaluation for hypogonadism included measurement of both total T and calculated free T levels. About 15% had low free T levels (<34 pg/mL) and thus were considered to have biochemical hypogonadism. Findings about sensitivity and specificity of total T as an indicator of biochemical hypogonad…