Description: IC50 Value: N/A Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and othervertebrates. in vitro: In rat aortic strips, 5-20 min treatment with physiological concentrations of testosterone significantly increased nitric oxide (NO) production. Testosterone modulates vascular EC growth and platelet aggregation through its direct action on endothelial NO production [1]. in vivo: The mean age was 39 years, and the mean pretreatment testosterone and estrogen levels were 247.6 +/- 39.8 ng/dL and 32.3 +/- 10.9, respectively. By the first follow-up visit (4-6 weeks), the mean testosterone level rose to 610.0 +/- 178.6 ng/dL (P < 0.00001). Moreover, the T/E ratio improved from 8.7 to 14.2 (P < 0.001) [2]. Serumtestosterone levels in three-quarter patients after surgical castration drop to less than 20ng/dl (0.69nmol/l). Ineffective suppression of testosterone is currently poorly recognized and may possibly have an effect of prostate cancer mortality [3]. Clinical trial: Safety and Efficacy Trial of Oral Testosterone Undecanoate (TU) in Hypogonadal Men. Phase 3