MEASURING FECAL ESTROGENS FOR THE DIAGNOSIS OF CRYPTORCHIDISM IN HORSES

The measurement of androgens and estrogens in blood has been widely ut ilized to differentiate geldings from horses with testicular tissue. E strogens are excreted in part via feces and can be quantified by immun oassay. Therefore a diagnosis of cryptorchidism based on the determina tion of fecal estrogens was established. The concentration of unconjug ated estrogens was measured in fecal samples of normal stallions (n=63 ), cryptorchid horses (n=34) and geldings (n=125). In addition the con centration of conjugated estrogens and testosterone in blood samples w as measured. Mature stallions had fecal estrogen concentrations in the range of 59 to 398 nmol/kg (median: 130) whereas that of geldings ran ged from I to 38 nmol/kg (median: 12). Stallions with one undescended testis (n=18) had concentrations of 60 to 322 nmol/kg (median: 113), w hich were indistinguishable from those of normal stallions. Fecal estr ogen concentrations of bilateral (n=9) and hemicastrated (n=7) cryptor chid horses ranged from 34 to 222 nmol/kg (median: 64) and differed (p <0.001) from those of stallions and geldings. By measuring fecal estro gens it was possible to detect testicular tissue in mature horses with good accuracy, similar to that by using steroid determinations in blo od. Therefore this study suggests that the determination of estrogens in feces is a useful tool for the diagnosis of equine cryptorchidism w ith an easy, noninvasive collection of samples.