Duan CW, et al. - Researchers here examined the association between testosterone and androstanediol glucuronide (AG), a reliable measure of androgen activity, in a nationally representative sample of US men. They identified a weak correlation between serum testosterone and total androgen activities. This correlation was even weaker for those with poor self-rated health. Results thereby suggest the significance of measuring total androgen activity in addition to testosterone in clinical practice, especially before administration of androgen replacement therapy.