Variability in total testosterone levels in ageing men with symptoms of androgen deficiency
Introduction: This study was conducted to assess variability in total testosterone levels (TT) in healthy, non-obese aging men who have androgen deficiency symptoms.
Methods: There were 96 men ≥55 years of age in the study. They were selected because they had symptoms consistent with androgen deficiency. Their morning TT levels were measured 4 times over 12 months.
Results: At each time point, geometric mean (95% confidence interval) of TT levels 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.
Sixty percent of the men differed by ≤1 nmol/L between sample 1 and 2. The maximum intra-individual TT difference between the 4 samples (interquartile range: 2.9-6.4) was 4.1 nmol/L. If an average of 2 baseline TT levels is used, then the maximum intra-individual difference is 2.3 nmol/L (interquartile range: 1.0-3.8).
Twenty-five men had a TT level < 10 nmol/L on at least one occasion during the study, but only 1 man had <10 nmol/L at all subsequent points; 8 of 9 men with an initial TT < 10 nmol/L had subsequent levels > 10 nmol/L. Only 2 of 35 men with an initial TT > 15 nmol/L had a subsequent value <10 nmol/L.
Conclusions: For healthy, non-obese aging men with androgen deficiency symptoms, a single TT level reliably predicts repeat measures taken over a 12-month period. However, intra-individual variability is sufficient to recommend a repeat sampling after an initially low TT level; this is particularly important since diagnosing androgen deficiency is dependent on the serum TT. Averaging 2 baseline TT levels can reduce the intra-individual variability.
This article seeks to determine the variability in total testosterone levels in healthy, non-obese aging men with symptoms of androgen deficiency.
The diagnosis of hypogonadism is determined by the presence of both sexual symptoms and low testosterone levels. It is well known that testosterone is secreted in a diurnal rhythm in young men and in some older men. Normal ranges are based upon early morning sampling. Repeated measurement of morning total testosterone levels is required to make a diagnosis of male hypogonadism.
Previous studies of healthy adult males as well as hypogonadal males reveal that significant individual variability of total testosterone exists (Morley et al, 2002; Swerdloff et al, 2000). It is important to understand the variability that exists in TT levels in the aging and symptomatic male population. This study showed considerable intra-subject variability in TT. It is, therefore, important to repeat testing in patients whose initial TT is low and to use the average of two baseline levels. Men with normal TT on initial testing are less likely to have subsequent low levels.