Purpose of review: Longitudinal studies of testosterone concentrations have yielded sharper estimates of age-related androgen declines than their cross-sectional counterparts. A potential explanation for this phenomenon is a secular (age independent) mechanism acting to accelerate within-individual testosterone decreases with time. This article reviews the evidence in favor of such secular trends and discusses potential causes and implications.
Recent findings: The magnitude of the proposed secular trend may be as much as 1% per calendar year in excess of per year cross-sectional trends. Current evidence suggests that body composition changes as expressed by BMI can in part account for the trend in testosterone. More speculative recent findings suggest a potential contributory role for environmental endocrine disruptors, but to date no longitudinal studies have examined this question. Symptomatic androgen deficiency as currently defined is associated with diverse downstream morbidity, but may not constitute a robust designation over longer term periods of time. Information concerning treatment patterns in the general population is limited.
Summary: Existing evidence, though limited, supports the hypothesis of secular declines in serum testosterone levels in adult men. It is conceivable that these trends may influence the health of the public. Studies confirming and accounting for these trends are needed.