Sexual behavior and serum concentrations of reproductive hormones in normal stallions

Recently, it has been reported that impotence in the stallion has a physiological basis that involves decreased serum concentrations of luteinizing hormone (LH) and estradiol-17β, but not testosterone. We have found such a hormonal profile in two of nine stallions studied during an ongoing investigation of the endocrinology of the normal stallion. Nevertheless, both of these stallions possessed vigorous libido and normal seminal characteristics. We conclude that the hormonal profile of low LH, low estradiol and normal testosterone, although it may accompany impotence in the stallion, is not predictive of, or causally related to, abnormalities in sexual behavior.