Seminal fructose, sperm count, and sperm motility were measured in 340 men attending an infertility clinic. Seminal fructose correlates negatively with sperm count but not with sperm motility. The best correlation between sperm count and seminal fructose was obtained using the logarithm (log) of sperm count. When seminal fructose was multiplied by the log of sperm count obtaining a value named "corrected fructose," the correlation with sperm count disappeared, and there was positive correlation between corrected seminal fructose and sperm motility. Therefore, corrected seminal fructose level was significantly lower in asthenospermic than in normomotile subjects, irrespective of the sperm count. Corrected seminal fructose, but not seminal fructose levels, was lowered in subjects with either low levels of serum testosterone ( < 3 ng/ml) or evidence of an obstructive process in the reproductive tract. In both situations sperm motility was also reduced. The corrected fructose level was not affected by the presence of varicocele, hyperprolactinemia, or hyperserotoninemia. Measurement of corrected seminal fructose rather than seminal fructose may be a useful marker of the secretory activity of the seminal vesicles.

Seventy men, aged 20-40 years, who were attending an infertility clinic were studied to evaluate associations between seminal quality, whole blood serotonin, and serum testosterone levels. Men with blood serotonin levels greater than 100 ng/ml showed lower sperm counts and sperm motility than those with normal levels of blood serotonin (less than 90 ng/ml). Seminal volume, pH, sperm morphology, fructose, citric acid, and serum testosterone values were similar between groups of patients with different levels of blood serotonin. The levels of blood serotonin correlated best with sperm motility when using a cubic regression analysis. When blood serotonin increased from 50 to 90 ng/ml (normal range), there was an increase in the percentage of spermatozoa with excellent motility. However, when serotonin was above 90 ng/ml the percentage of sperm with excellent motility decreased. An inverse exponential relationship was observed between blood serotonin and sperm count. The sperm count reached values of oligozoospermia when blood serotonin was over 100 ng/ml. It would appear that blood serotonin in the normal range is important for sperm motility. Values of serotonin above the normal range could affect negatively both sperm count and motility. These effects were observed in the absence of changes in serum testosterone levels.