Variability in total testosterone levels in ageing men with symptoms of androgen deficiency

The aim of this study was to determine the variability in total testosterone (TT) levels in healthy, non-obese ageing men with symptoms of androgen deficiency. Men aged ≥55 years were recruited from the community. Morning TT levels were measured on four occasions in a 12-month period. In all, 96 men aged 62.7 ± 6.8 years were studied. Geometric mean values (95% confidence interval) of TT levels for the cohort at each time point were 14.5 (13.4-15.7), 14.6 (13.5-15.8), 15.5 (14.4-16.8) and 15.0 (13.9-16.2) nmol/L. The maximum intra-individual difference in TT between the four samples was 4.1 nmol/L (interquartile range: 2.9-6.4). Using the average of two baseline TT values reduces the maximum difference to 2.3 nmol/L (1.0-3.8). Only 1 of 25 men with a documented TT <10 nmol/L at baseline had TT levels <10 nmol/L at all subsequent time points. A single TT level is a reliable predictor of repeat measures taken within a 12-month period for a cohort of healthy ageing men with symptoms of androgen deficiency. However, given that the diagnostic criteria for androgen deficiency are, in part, predicated upon serum TT, there is sufficient intra-subject variability to warrant repeat sampling to confirm an initial low TT level. Using an average of two baseline TT values reduces this variability.