Objective: To determine serum concentrations, intra-individual variability and impact of age-related co-morbidities on serum testosterone (T), dihydrotestosterone (DHT), estradiol (E(2)) and estrone (E(1)) in older men.
Design: Observational, repeated measures study.
Participants: Men (n = 325) with 40 years and older self-reporting very good or excellent health.
Measurements: Standardized history, physical examination and collection of nine blood samples at fixed time intervals were measured over 3 months (three at 20 min intervals on days 1 (fasting) and 2 (non-fasting), one at days 7, 30 and 90). Serum T, DHT, E(2) and E(1) (n = 2900, > 99% of scheduled samples) measured by liquid chromatography-tandem mass spectrometry (LC-MS) were analysed by linear mixed model analysis with fasting, age and obesity as covariables.
Results: Mean serum T did not vary with age (P = 0·76) but obesity (-0·35 nM per body mass index (BMI) unit, P < 0·0001) and ex-smoker status (-1·6 nM, P < 0·001) had significant effects. Serum DHT was increased with age (+0·011 nM per year, P = 0·001) but decreased with obesity (-0·05 nM per BMI unit, P < 0·0001). Serum E(2) did not vary with age (P = 0·31) or obesity (P = 0·12). Overnight fasting increased (by 9-16%, all P < 0·001) and reduced variability in morning serum T, DHT, E(2) and E(1). Non-fasting serum T and DHT were stable over time (day, week, month or 3 months; P > 0·28).
Conclusions: Serum T, DHT and E(2) displayed no decrease associated with age among men over 40 years of age who self-report very good or excellent health although obesity and ex-smoking status were associated with decreased serum androgens (T and DHT) but not E(2). These findings support the interpretation that the age-related decline in blood T accompanying non-specific symptoms in older men may be due to accumulating age-related co-morbidities rather than a symptomatic androgen deficiency state.
© 2012 Blackwell Publishing Ltd.