The aim of this study was to evaluate the age changes of both total and free testosterone levels in 186 adult, healthy and occupationally active Polish men, aged between 22 and 67. Free and total testosterone levels were measured by means of standard immunoassay kits. Since the distribution of hormonal parameters differed from normal, non-parametric statistical analyses (Spearman coefficient) were used. Free testosterone levels reached peak values in the 30-34 year age category (21.1 pg/ml), while a decline of total testosterone began in 22-24 yr old males (6.15 ng/ml). Afterwards, they both began to decrease gradually with age. Free and total testosterone levels strongly correlate with age (respectively r=-0.478; p=0.000 for free testosterone and r=-0.251; p=0.0005 for total testosterone). Initial values (maximal age levels) of total testosterone were reduced by 45%, while that of free testosterone by 40% in men aged 55 and older. Free testosterone concentrations demonstrated a relatively regular decrease during the investigated period, whereas a progressive decline of total testosterone levels was disturbed about the age of 45 yrs by an unexpected rapid increase of its concentrations to values of 5.7 ng/ml, similar to those observed in men, aged between 25 and 29. An endocrinological interpretation of this phenomenon remains unclear. Our study confirmed the marginal importance of total testosterone levels in comparison with free testosterone concentrations in the diagnostics of andropausal hypogonadism.

Keywords: male aging, free and total testosterone levels, andropause