(121) Population Reference Values for Total Testosterone in Brazilian Men: Evidence of Stability Across Aging

Introduction Age-related androgen decline is traditionally described as a gradual and multifactorial process; however, its magnitude and clinical relevance remain controversial due to high interindividual variability and the frequent absence of symptoms. ~In Brazil, population-based laboratory data describing total testosterone (T) distribution by age are scarce.~ Population-based laboratory data on total testosterone (T) distribution by age in Brazilian men are limited.a gradual and multifactorial process; however, Objective To characterize median T values, dispersion, and the frequency of low T across age groups in Brazilian men aged 40–79 years, providing reference parameters for clinical practice and research. Methods We conducted a cross-sectional analysis of 4,699 routine total testosterone (T) measurements in men aged 40–79 years. Participants were stratified into four age bands (40–49, 50–59, 60–69, 70–79 years). For each group, we calculated median T, interquartile range (IQR), and the proportion of results <300 ng/dL to describe central tendency, dispersion, and the frequency of biochemically low T. The association between age (continuous) and T levels was examined using Pearson’s correlation coefficient. Descriptive and inferential analyses were performed with standard statistical software, and all tests were two-tailed with significance set at p < 0.05.The median T, interquartile range (IQR), and the proportion of results <300 ng/dL to describe central tendency, dispersion, and the frequency of biochemically low T levels. Results The overall median T was 445 ng/dL (IQR, 336–577). Median values by age group were 424 [326–542], 431 [328–561], 458 [345–589], and 454 [340–592] ng/dL for 40–49 (n=1,071), 50–59 (n=1,888), 60–69 (n=1,740), and 70–79 years (n=1,060), respectively. The prevalence of T <300 ng/dL was 14.8%, 12.6%, 10.6%, and 12.2% across these groups. A weak positive correlation was observed between age and T (r = 0.082; p < 0.0001), with progressive interindividual dispersion in older strata. Contrary to the expected age-related decline, median T levels were stable or slightly higher in older groups, with broader variability. Conclusions In this large sample of Brazilian men aged 40–79 years, total testosterone (T) levels did not decline with aging. ~Instead, a paradoxical pattern of stable or slightly higher median T and greater interindividual dispersion was observed in older groups.~ Older men showed similar or higher median T, alongside greater dispersion. Age played only a minor role in determining T concentrations, suggesting that clinical, metabolic, and individual factors may exert greater influence on androgen status. These data provide age-stratified reference values that can inform diagnostic thresholds, guide therapeutic decision-making in urology and endocrinology, and support future studies on hypogonadism and testosterone replacement. Disclosure No