Methods for predicting sexual maturity in male cynomolgus macaques on the basis of age, body weight, and histologic evaluation of the testes.

In pharmaceutical drug safety testing, sexual maturity is an important experimental parameter. Histologic immaturity of the tissues of the reproductive system can interfere with the interpretation of compound-related effects on the reproductive organs. In female cynomolgus macaques, determination of sexual maturity is simplified by the presence of a menstrual cycle. For male cynomolgus macaques, predicting maturity is much more difficult. In this study, we evaluated methods that would reliably predict sexual maturity in male cynomolgus macaques. The results of histologic examination of testes of control male cynomolgus macaques used for drug safety studies were examined retrospectively for evidence of sexual maturity. These data were compared with age and body weight determinations to establish statistical models for determining the probability that a male cynomolgus macaque is sexually mature. This model presents a simple prospective method of predicting sexual maturity in male cynomolgus macaques.