Objective non-intrusive markers of sperm production and sexual activity

Abstract

Objective studies of men's reproductive function are hindered by their reliance on: (i) self-reporting to quantify sexual activity and (ii) masturbation to quantify sperm output rendering both types of estimate vulnerable to unverifiable subjective factors. We therefore examined whether detection of spermatozoa and measurement of prostate-specific antigen (PSA) in urine could provide objective semiquantitative estimates of sperm output and recent ejaculation, respectively, using widely available laboratory techniques. Of 11 healthy volunteers who provided urine samples before and at intervals for 5 days after ejaculation, sperm was present in 2/11 men before, and in all 11/11 samples immediately after ejaculation, but by the second and subsequent void, spermatozoa were present in ∼10%. PSA was detectable at high levels in all urine samples, peaking at the first post-ejaculatory sample but returning to baseline levels by the second post-ejaculatory void. We conclude that urinary spermatozoa and PSA are objective biomarkers for sperm production and sexual activity, but only for a short-time window until the first post-ejaculatory urine void. Hence, for a single urine specimen, the presence of spermatozoa and PSA are valid biomarkers, reflecting sperm production and recent ejaculation only until the next micturition, so their measurement should be restricted to the first morning urine void.

Figure 1

Study 1. Histogram displaying the proportion of 11 men with urine specimens positive for spermatozoa before (PRE) and at intervals after ejaculation. P1 was the first post-ejaculatory void which was further fractionated into five serially-voided aliquots for the first five men only. The subsequent voids P2–P5 were within the first day after ejaculation and D2–D5 were the urine samples on the second to fifth day post ejaculation. Further details are shown in Table 1. PRE, pre-ejaculatory urine specimen.

Figure 2

Study 1. Plot of urinary PSA concentration before and at various voids after ejaculation. Note logarithmic y axis scale. Individual men's samples are connected by dotted lines and the solid line is a smoothed spline plot of the median PSA level for each set of void samples. P6 represents 2 men who provided a 6th post-ejaculatory urine sample within the first 24 h post-ejaculation. Further details are shown in Table 2. PSA, prostate-specific antigen.

Figure 3

Study 1. Histogram of the proportion of men whose urinary PSA was increased or decreased relative to their pre-ejaculation baseline at various post-ejaculation time points. PSA, prostate-specific antigen.

Figure 4

Study 2. Plot of urinary PSA concentration against time since last ejaculation in 100 urine samples from 84 men undergoing routine semen analysis. Note data for 1 day of abstinence include men with less than 24 h abstinence. PSA, prostate-specific antigen.