Testicular and glandular contributions to the prolactin pool in human semen

The immunoreactive prolactin in human seminal plasma originates predominantly from two sources, the seminal vesicles and the testicular-epididymal axis. The following evidence supported a testicular-epididymal origin: (1) Vasectomy reduced the content of prolactin in the ejaculates by 50%; (2) the concentration of seminal prolactin was highly correlated (r = 0.54, p < 0.003) with the concentration of sperm in a normal population of young and middle-aged men; and (3) prolactin concentrations in the split ejaculates of normospermic men revealed a profile that corresponded to the sperm distribution pattern. Evidence supporting an additional contribution from the seminal vesicles included the following. (1) The split ejaculate of an azoospermic individual coincided more with the distribution of the vesicular parameter fructose; (2) vasectomy did not cause the disappearance of prolactin from the ejaculate; and (3) split-ejaculate analyses weakened the possibility of a major prostatic source.