3 FULL SISTER MARES WITH A STALLION-LIKE BEHAVIOR AND A HIGH BLOOD TESTOSTERONE CONCENTRATION - A CASE-REPORT

The testosterone concentration was very high in a 6-year-old maiden ma re. The mare showed a typical male behavior. She appeared to have two full sisters with the same abnormal behavior. The mare's external geni talia were normal, whereas the internal genitalia were abnormal: no ce rvix and no uterus, the gonads resembled a testis. The resting plasma testosterone concentration was 0.76 ng/ml. The results of the HCG stim ulation test are shown in Table 1. The response to HCG administration was poor. Karyotyping of 50 metaphase plates showed a normal female ka ryotype of 2N = 64 XX.