Seminal plasma melatonin and gonadal steroids concentrations in normal men.

The authors determined semen quality and the concentrations of estradiol, testosterone, and melatonin in blood and seminal plasma of 8 normal men. To investigate the reproducibility of these parameters, semen analysis and hormone concentrations were determined on 3 occasions, 6 weeks apart. All 8 men had normal semen analysis. Blood melatonin (9.7-45.4 pg/mL) and testosterone (3.5-12.3 ng/mL) levels were significantly higher than the comparable seminal plasma levels (0.6-5.0 pg/mL, p <.02; 0.1-0.9 ng/mL, p <.0001, respectively). Seminal plasma estradiol levels (46.9-91.3 pg/mL) were significantly higher than the blood levels (13.3-44.7 pg/mL) (p <.0001). The intraindividual variations in seminal plasma estradiol levels ranged between 8.7 and 13.8%. There was no correlation between sperm concentration, motility or morphology and blood or seminal plasma hormone levels. Also, blood and seminal plasma hormone levels were not correlated. These results indicate that in normospermic men seminal plasma estradiol levels are higher than blood hormone levels, suggesting local production of estradiol. This may imply that estrogen and/or the balance andorgen/estrogen is important in normal human spermatogenesis.