Normal, bound and nonbound testosterone levels in normally ageing men: results from the Massachusetts Male Ageing Study

Age, health and lifestyle factors impact androgen levels and should be accounted for in calculations of normal reference ranges. We propose the following age-specific thresholds, below which a man is considered to have an abnormally low total T: 8.7, 7.5, 6.8 and 5.4 nm (251, 216, 196 and 156 ng/dl) for men in their 40s, 50s, 60s and 70s, respectively. These cutoffs correspond to the 2.5th percentile in our data; thus, approximately 2.5% of men aged 40-79 years would have abnormally low T levels based on hormone levels alone.