Age-related decline in total testosterone levels among young men: insights from a large single-center observational study.

We aimed to depict the age-specific distribution of total Testosterone (tT) levels among young men presenting to a single academic centre with uro-andrological complaints. Overall, tT levels from 2593 men aged 20-44 years were analyzed. Men were grouped into 'infertile men' and 'men with sexual dysfunction (SD)' according to their primary complaints. Data was also collected from 71 same-ethnicity age-comparable fertile controls. Linear regression fitted the relationship between tT and increasing age. Distribution of tT was determined for each 5-year age-group, both for the overall population and the subgroups. tT quantiles were reported for each sample sub-group and age-group. Of 2664 men, 1913 (71.81%) were classified as infertile, 680 (25.52%) with SD and 71 as fertile men (2.67%), respectively. tT levels depicted a reduction of 0.14 nmol/L per year between 20 and 44 years of age (p < 0.001) within the overall study population. Significant reduction was also observed for the population stratified by urological complaints (all p < 0.05). This is the first study to describe tT levels as a function of baseline clinical status in a large same-ethnicity cohort of young men, uniformly assessed using a standardized laboratory method.