Abstract
The measurement of bioavailable testosterone (BT) or free testosterone (FT) levels is currently considered the gold standard for the diagnosis of androgen deficiency in elderly men. While the impact of age on circulating testosterone levels (total, bioavailable and free) has been strongly documented, the existence of seasonal variations in testosterone levels remains debated.
We investigated whether seasonal variations in serum calculated free testosterone (cFT) levels may translate into variations in the prevalence of low testosterone levels. Diagnosis was on the basis of biochemical determinations and was cross-checked with the prevalence of clinical signs and symptoms of ‘andropause’, as assessed by the Androgen Deficiency in Aging Males (ADAM) questionnaire.
The study recruited 5028 men aged 50 years and over from September 2000 to January 2003. Their serum FT levels were assessed and they completed the French ADAM test. Men were considered eugonadal when cFT was ≥70
ng/l. The ADAM test was scored as described originally. The prevalence of ‘andropause’, diagnosed by the two methods, was compared throughout the year, on a month by month basis.
The percentage of subjects with cFT levels below 70
ng/l increased significantly with age (
P<0.001). Serum cFT levels (mean [SD]) varied significantly with the month of sampling (
P<0.0001), the highest (88.1 [30.2] ng/l) and lowest (76.9 [28.0] ng/l) mean values occurring in April and in October, respectively. Conversely, the prevalence of testosterone deficiency (cFT<70
ng/l) reached a peak in October (45.7%) and a nadir in April (29.7%). Although the prevalence of ‘andropause’, based on the ADAM questionnaire, increased significantly with age (
P<0.0001), no influence of the month of the year was noticed.
Our results confirm a progressive age-related decline in FT levels. The monthly variations in serum FT values, observed throughout the year, do not show a major seasonal rhythm in elderly community-dwelling males, since the magnitude of the variations (<15%) remains marginal. This slight variation may, however, have an impact on the number of elderly men diagnosed with Partial Androgen Deficiency in Aging Males (PADAM).