Changes in peripheral plasma luteinizing hormone and testosterone concentrations and semen quality in normal and cryptorchid dogs during sexual maturation.

Changes in peripheral plasma luteinizing hormone (LH) and testosterone (T) concentrations and semen quality were investigated in four unilaterally cryptorchid (UC), three bilaterally cryptorchid (BC), and five normal beagles, from 4 to 48 weeks of age. Blood samples were collected at 2- or 4-week intervals, and the LH and T concentrations were determined by radioimmunoassay. Semen samples were collected weekly by digital manipulation. The mean LH and T concentrations in the normal dogs increased after 20 and 22 weeks of age and reached approximately 4 ng/ml and 3 ng/ml respectively at 36 weeks of age. Semen volume and total spermatozoa count increased apparently at 34 and 35 weeks of age respectively. Spermatozoa motility and percentage of abnormal spermatozoa varied less after 38 weeks of age. Plasma LH and T concentrations in the UC and BC dogs had a tendency to remain lower than values in the normal dogs after 26 weeks of age. The semen volume and spermatozoa count in the UC dogs did not increase markedly. The spermatozoa count was less than half that in normal dogs, and the percentage of abnormal spermatozoa was higher throughout the experimental period. All BC dogs had azoospermia. Thus it was evident that development of spermatogenic function during sexual maturation in the UC and BC dogs was insufficient compared with that in normal dogs.