Effect of oral chronic isoflavones supplementation on male rat sexual performances and sexual hormone plasma levels.

The aim of our study was to evaluate how a chronic isoflavones oral supplementation could affect male rat sexual behavior in relationship to cause eventual change in plasma sexual hormone concentrations. Isoflavones were administered in the form of a standardized dry extract of soybeans. Three groups of 20 sexually experienced male rats were consecutively treated with saline 2 ml, or isoflavones 0.4 mg/kg(-1) or 0.8 mg/kg(-1) soybean dried extract via gastric tube for 40 days. No significant differences were found as regards sexual performances of the three studied groups at the baseline levels nor at the end of the study: in relationship to the base-line value, only mount frequency increased in the control group (z = -2.047, p = 0.041), while intromission frequency in the high dosage isoflavones group (z = -2.484, p = 0.13). At the base-line test 23.08% of rats in each group were not able to conclude their performance in the standard time, while at the end of the study only 15.38% of the control group rats were not able to do this. No significant difference has been observed as regards FSH, progesterone, androstenedione plasma levels, either between groups or between baseline and study end. Slight differences were found regards LH and testosterone plasma level. Copyright 2004 John Wiley & Sons, Ltd.