Frequently subnormal semen profiles of normal volunteers recruited over 17 years.

In order to establish semen profiles for men in the general population, we analysed the semen parameters of 187 men attending the Institute of Reproductive Medicine between 1977 and 1993 as volunteers for clinical studies. If several ejaculates were obtained from the volunteer, only the first ejaculate was used for analysis. More than half of the ejaculates of these healthy men showed at least one abnormal parameter, so that only 46% of the volunteers could be classified as being 'normozoospermic' according to WHO guidelines. Aside from a decrease in the proportion of motile spermatozoa, no change in semen parameters could be detected with advancing age of the volunteers. No negative influence of the presence of a varicocele, the grade of varicocele on a history of maldescended testis on semen parameters was detected. The serum levels of FSH, LH and testosterone showed no significant age-related change over the period of investigation. Follow-up analysis of the fertility on the volunteers revealed a proportion of unwanted barrenness similar to or even lower than that in the general population. The analysis demonstrates that the limits of normality for semen parameters may require redefinition.